ready4 – Use - utility mapping

Docs: Examples

Thu, 05 Jan 2017 00:00:00 +0000

An scientific summary of the ready4 prototype software framework and its early application in youth mental health is available as an open-access article in PharmacoEconomics.

Additional information is available from the project website of readyforwhatsnext - a modular and open source economic model of youth mental health.

Docs: Model health utility

Thu, 05 Jan 2017 00:00:00 +0000

Docs: Explore candidate utility mapping models

Fri, 20 Oct 2023 00:00:00 +0000

This below section renders a vignette article from the specific library. You can use the following links to:

view the vignette on the library website (adds useful hyperlinks to code blocks)
view the source file from that article, and;
edit its contents (requires a GitHub account).

Note: This vignette uses fake data - it is for illustrative purposes only and should not be used to inform decision making. The specific package includes ready4 framework model modules that form part of the ready4 youth mental health economic model. Currently, these modules are not optimised to be used directly, but are instead intended for use in other model modules. For example, the TTU package includes modules that extend specific modules to help implement utility mapping studies. However, to illustrate the main features of specific modules this vignette demonstrates how specific modules could be used independently. In practice, workflow illustrated in this article would probably need to be performed iteratively in order to identify the optimal model types, predictors and covariates and to update default values to ensure model convergence.

library(ready4)
library(scorz)
library(specific)

By default, modules in the specific package will request your consent before writing files to your machine. This is the safest option. However, as there are many files that need to be written locally for this program to execute, you can overwrite this default by supplying the value “Y” to methods with a consent_1L_chr argument.

consent_1L_chr <- "" # Default value - asks for consent prior to writing each file.

Import data

We start by ingesting our data. As this example uses EQ-5D data, we import a ScorzEuroQol5 ready4 framework module (created using the steps described in this vignette from the scorz pacakge) into a SpecificConverter Module and then apply the metamorphose method to convert it into a SpecificModel module.

X <- SpecificConverter(a_ScorzProfile = ready4use::Ready4useRepos(gh_repo_1L_chr = "ready4-dev/scorz", 
                                                                  gh_tag_1L_chr = "Documentation_0.0") %>%
                         ingest(fls_to_ingest_chr = "ymh_ScorzEuroQol5",  metadata_1L_lgl = F)) %>% 
  metamorphose()

class(X)
#> [1] "SpecificModels"
#> attr(,"package")
#> [1] "specific"

Inspect data

The dataset we are using has a total of 1786 records at two timepoints on 1068 study participants. The first six records are reproduced below.

Dataset
Unique identifier	Data collection round	Date of data collection	Age	Gender (grouped)	Sex at birth	Sexual orientation	Relationship status	Aboriginal or Torres Strait Islander	Culturally And Linguistically Diverse	Region of residence (metropolitan or regional)	Education and employment status	EQ5D - Mobility domain score	EQ5D - Self-Care domain score	EQ5D - Usual Activities domain score	EQ5D - Pain / Discomfort domain score	EQ5D - Anxiety / Depression domain score	Kessler Psychological Distress - 10 Item Total Score	Overall Wellbeing Measure (Winefield et al. 2012)	EuroQol (EQ-5D) - (weighted total)	EuroQol (EQ-5D) - (unweighted total)
1	BL	2019-10-22	14	Male	Male	Heterosexual	In a relationship	No	No	Metro	Not studying or working	1	1	1	1	2	11	87	0.879	6
2	BL	2019-10-17	19	Female	Female	Heterosexual	In a relationship	Yes	Yes	Regional	Studying only	1	2	1	1	1	14	65	0.846	6
2	FUP	2020-02-14	19	Female	Female	Heterosexual	In a relationship	Yes	Yes	Regional	Studying only	3	1	1	1	1	10	71	0.850	7
3	BL	2020-02-15	21	Female	Female	Other	Not in a relationship	NA	NA	Metro	Studying only	1	1	3	1	1	13	74	0.883	7
3	FUP	2020-06-14	21	Female	Female	Other	Not in a relationship	NA	NA	Metro	Studying only	1	1	2	1	1	10	64	0.906	6
4	BL	2019-12-14	12	Female	Female	Heterosexual	In a relationship	Yes	Yes	Metro	Not studying or working	1	1	1	3	1	18	40	0.796	7

To source dataset of X is contained in the a_YouthvarsProfile slot and is a YouthvarsSeries module. For more information about methods that can be used to explore this dataset, read this vignette from the youthvars package.

Specify parameters

In preparation for exploring our dataset, we need to declare a set of model parameters in a b_SpecificParameters slot of X. This can be done in one step, or in sequential steps. In this example, we will proceed sequentially.

Dependent variable

The dependent variable (total EQ-5D utility score) has already been specified when we imported the data from the ScorzEuroQol5 module.

procureSlot(X, "b_SpecificParameters@depnt_var_nm_1L_chr")
#> [1] "eq5d_total_w"

We can now add details of the allowable range of dependent variable values.

X <- renewSlot(X, "b_SpecificParameters@depnt_var_min_max_dbl", c(-1,1))

Candidate predictors

We can now specify the names of candidate predictor variables.

X <- renewSlot(X, "b_SpecificParameters@candidate_predrs_chr", c("K10_int","Psych_well_int"))

We next add meta-data about each candidate predictor variable in the form of a specific_predictors object.

X <- renewSlot(X, "b_SpecificParameters@predictors_lup", class_chr = "integer", class_fn_chr = c("youthvars::youthvars_k10_aus","as.integer"), covariate_lgl = F, increment_dbl = 1,
               long_name_chr = c("Kessler Psychological Distress - 10 Item Total Score", "Overall Wellbeing Measure (Winefield et al. 2012)"), max_val_dbl = c(50,90), min_val_dbl = c(10,18), mdl_scaling_dbl = 0.01,
               short_name_chr = c("K10_int","Psych_well_int"))

The specific_predictors object that we have added to X can be inspected using the exhibitSlot method.

exhibitSlot(X, "b_SpecificParameters@predictors_lup", scroll_box_args_ls = list(width = "100%"))

Variable	Description	Minimum	Maximum	Class	Increment	Function	Scaling	Covariate
K10_int	Kessler Psychological Distress - 10 Item Total Score	10	50	integer	1	youthvars::youthvars_k10_aus	0.01	FALSE
Psych_well_int	Overall Wellbeing Measure (Winefield et al. 2012)	18	90	integer	1	as.integer	0.01	FALSE

Covariates

We also specify the covariates that we aim to explore in conjunction with each candidate predictor.

X <- renewSlot(X, "b_SpecificParameters@candidate_covars_chr", c("d_sex_birth_s", "d_age",  "d_sexual_ori_s", "d_studying_working"))

Descriptive variables

We also specify variables that we will use for generating descriptive statistics about the dataset.

X <- renewSlot(X,"b_SpecificParameters@descv_var_nms_chr", c("d_age","Gender","d_relation_s", "d_sexual_ori_s", "Region", "d_studying_working"))

Temporal variables

The name of the dataset variable for data collection timepoint and all of its unique values were imported when converting the ScorzEuroQol5 module.

procureSlot(X,"a_YouthvarsProfile@timepoint_var_nm_1L_chr")
#> [1] "Timepoint"

procureSlot(X,"a_YouthvarsProfile@timepoint_vals_chr")
#> [1] "BL"  "FUP"

However, we also need to specify the name of the variable that contains the datestamp for each dataset record.

X <- renewSlot(X, "b_SpecificParameters@msrmnt_date_var_nm_1L_chr", "data_collection_dtm")

Candidate models

X was created with a default set of candidate models, stored as a specific_models sub-module, which can be inspected using the exhibitSlot method.

exhibitSlot(X, "b_SpecificParameters@candidate_mdls_lup", scroll_box_args_ls = list(width = "100%"))

Model types lookup table
Reference	Name	Control	Familty	Function	Start	Predict	Transformation	Binomial	Acronym (Fixed)	Acronymy (Mixed)	Type (Mixed)	With
OLS_NTF	Ordinary Least Squares (no transformation)	NA	NA	lm	NA	NA	NTF	FALSE	OLS	LMM	linear mixed model	no transformation
OLS_LOG	Ordinary Least Squares (log transformation)	NA	NA	lm	NA	NA	LOG	FALSE	OLS	LMM	linear mixed model	log transformation
OLS_LOGIT	Ordinary Least Squares (logit transformation)	NA	NA	lm	NA	NA	LOGIT	FALSE	OLS	LMM	linear mixed model	logit transformation
OLS_LOGLOG	Ordinary Least Squares (log log transformation)	NA	NA	lm	NA	NA	LOGLOG	FALSE	OLS	LMM	linear mixed model	log log transformation
OLS_CLL	Ordinary Least Squares (complementary log log transformation)	NA	NA	lm	NA	NA	CLL	FALSE	OLS	LMM	linear mixed model	complementary log log transformation
GLM_GSN_LOG	Generalised Linear Model with Gaussian distribution and log link	NA	gaussian(log)	glm	-0.1,-0.1	response	NTF	FALSE	GLM	GLMM	generalised linear mixed model	Gaussian distribution and log link
BET_LGT	Beta Regression Model with Binomial distribution and logit link	betareg::betareg.control	NA	betareg::betareg	-0.5,-0.1,3	response	NTF	FALSE	GLM	GLMM	generalised linear mixed model	Binomial distribution and logit link
BET_CLL	Beta Regression Model with Binomial distribution and complementary log log link	betareg::betareg.control	NA	betareg::betareg	-0.5,-0.1,3	response	NTF	FALSE	GLM	GLMM	generalised linear mixed model	Binomial distribution and complementary log log link

We can choose to select just a subset of these to explore using the renewSlot method. As this is an illustrative example, we have restricted the models we will explore to just four types, passing the relevant row numbers to the slice_indcs_int argument.

X <- renewSlot(X, "b_SpecificParameters@candidate_mdls_lup", slice_indcs_int = c(1L,5L,7L,8L))

Other parameters

Depending on the type of analysis we plan on undertaking, we can also specify parameters such as the number of folds to use in cross validation, the maximum number of model runs to allow and a seed to ensure reproducibility of results. In this case we are going to use the default values generated when we first created X.

procureSlot(X, "b_SpecificParameters@folds_1L_int")
#> [1] 10

procureSlot(X, "b_SpecificParameters@max_mdl_runs_1L_int")
#> [1] 300

procureSlot(X, "b_SpecificParameters@seed_1L_int")
#> [1] 1234

Model testing

Before we start to use the data stored in X to undertake modelling, we must first validate that it contains all necessary (and internally consistent) data by using the ratify method. The call to ratify will update any variable names that are likely to cause problems when generating reports (e.g. through inclusion of characters like “_” in the variable name that can cause problems when rendering LaTeX documents).

X <- ratify(X)

Set-up workspace

We add details of the directory to which we will write all output. In this example we create a temporary directory (tempdir()), but in practice this would be an existing directory on your local machine.

X <- renewSlot(X, "paths_chr", tempdir())

It can be useful to save fake data (useful for demonstrating the generalisability and replicability of an analysis) and real data (required for write-up and reproducibility) is distinctly labelled directories. By default, X is created with a flag to save all output in a sub-directory “Real”. As we are using fake data, we can override this value.

X <- renewSlot(X, "b_SpecificParameters@fake_1L_lgl", T)

We can now write a number of sub-directories to our specified output directory.

X <- author(X, what_1L_chr = "workspace", consent_1L_chr = consent_1L_chr)
#> New directories created:
#> C:\Users\mham0053\AppData\Local\Temp\RtmpQBtivk/Fake
#> C:\Users\mham0053\AppData\Local\Temp\RtmpQBtivk/Fake/Markdown
#> C:\Users\mham0053\AppData\Local\Temp\RtmpQBtivk/Fake/Output
#> C:\Users\mham0053\AppData\Local\Temp\RtmpQBtivk/Fake/Reports
#> C:\Users\mham0053\AppData\Local\Temp\RtmpQBtivk/Fake/Output/_Descriptives
#> C:\Users\mham0053\AppData\Local\Temp\RtmpQBtivk/Fake/Output/H_Dataverse

Descriptives

The first set of outputs we write to our output directories is a set of descriptive tables and plots.

X <- author(X, consent_1L_chr = consent_1L_chr, digits_1L_int = 3L,  what_1L_chr = "descriptives")

Model comparisons

The investigate method can now be used to compare the candidate models we have specified earlier. In so doing it will transform X into a SpecificPredictors object.

X <- investigate(X, consent_1L_chr = consent_1L_chr, depnt_var_max_val_1L_dbl = 0.99, session_ls = sessionInfo())

class(X)
#> [1] "SpecificPredictors"
#> attr(,"package")
#> [1] "specific"

The investigate method will write each model to be tested to a new sub-directory of our output directory.

The investigate method also outputs a table summarising the performance of each of the candidate models.

exhibit(X, what_1L_chr = "mdl_cmprsn", type_1L_chr = "results")

Comparison of candidate models using highest correlated predictor
	Training model fit (averaged over 10 folds)	Testing model fit (averaged over 10 folds)
Model	R-Squared	RMSE	MAE	R-Squared	RMSE	MAE
Beta Regression Model with Binomial distribution and logit link	0.4318533	0.0742448	0.0587307	0.4128497	0.0741236	0.0587733
Beta Regression Model with Binomial distribution and complementary log log link	0.4174181	0.0751836	0.0593447	0.3996947	0.0750880	0.0594047
Ordinary Least Squares (no transformation)	0.4106104	0.0756222	0.0596955	0.3933147	0.0755461	0.0597672
Ordinary Least Squares (complementary log log transformation)	0.4105040	0.0756284	0.0597793	0.3913360	0.0755268	0.0598295

We can now identify the highest performing model in each category of candidate model based on the testing R² statistic.

procure(X, what_1L_chr = "prefd_mdls") 
#> [1] "BET_LGT" "OLS_NTF"

We can override these automated selections and instead incorporate other considerations (possibly based on judgments informed by visual inspection of the plots and the desirability of constraining predictions to a maximum value of one). We do this in the following command, specifying new preferred model types, in descending order of preference.

X <- renew(X, new_val_xx = c("BET_LGT", "OLS_CLL"), type_1L_chr = "results", what_1L_chr = "prefd_mdls")

Use most preferred model to compare all candidate predictors

We can now compare all of our candidate predictors (with and without candidate covariates) using the most preferred model type.

X <- investigate(X, consent_1L_chr = consent_1L_chr)

class(X)
#> [1] "SpecificFixed"
#> attr(,"package")
#> [1] "specific"

Now, we compare the performance of single predictor models of our preferred model type (in our case, a Beta Regression Model with Binomial distribution and logit link) for each candidate predictor. The last call to the investigate saved the tested models along with model plots in a sub-directory of our output directory. These results are also viewable as a table.

exhibit(X, scroll_box_args_ls = list(width = "100%"), type_1L_chr = "results", what_1L_chr = "predr_cmprsn")

Comparison of all candidate predictors using preferred model
predr_chr	%IncMSE	IncNodePurity
K10	0.0066197	3.888246
Psychwell	0.0011094	2.342784

The most recent call to the investigate method also saved single predictor R model objects (one for each candidate predictors) along with the two plots for each model in a sub-directory of our output directory. The performance of each single predictor model can also be summarised in a table.

exhibit(X, type_1L_chr = "results", what_1L_chr = "fxd_sngl_cmprsn")

Preferred single predictor model performance by candidate predictor
	Training model fit (averaged over 10 folds)	Testing model fit (averaged over 10 folds)
Model	R-Squared	RMSE	MAE	R-Squared	RMSE	MAE
K10	0.4318533	0.0742448	0.0587307	0.4128497	0.0741236	0.0587733
Psychwell	0.1507472	0.0907813	0.0699606	0.1341090	0.0909203	0.0700686

Updated versions of each of the models in the previous step (this time with covariates added) are saved to a new subdirectory of the output directory and we can summarise the performance of each of the updated models, along with all signficant model terms, in a table.

exhibit(X, scroll_box_args_ls = list(width = "100%"), type_1L_chr = "results", what_1L_chr = "fxd_full_cmprsn")

We can now identify which, if any, of the candidate covariates we previously specified are significant predictors in any of the models.

procure(X, type_1L_chr = "results", what_1L_chr = "signt_covars")
#> [1] NA

We can override the covariates to select, potentially because we want to select only covariates that are significant for all or most of the models. However, in the below example we have opted not to do so and continue to use no covariates as selected by the algorithm in the previous step.

# X <- renew(X, new_val_xx = c("COVARIATE OF YOUR CHOICE", "ANOTHER COVARIATE"), type_1L_chr = "results", what_1L_chr = "prefd_covars")

Test preferred model with preferred covariates for each candidate predictor

We now conclude our model testing by rerunning the previous step, except confining our covariates to those we prefer.

X <- investigate(X, consent_1L_chr = consent_1L_chr)

class(X)
#> [1] "SpecificMixed"
#> attr(,"package")
#> [1] "specific"

The previous call to the write_mdls_with_covars_cmprsn function saves the tested models along with two plots for each model in the “E_Predrs_W_Covars_Sngl_Mdl_Cmprsn” sub-directory of “Output”.

Apply preferred model types and predictors to longitudinal data

The next main step is to use the preferred model types and covariates identified from the preceding analysis of cross-sectional data in longitudinal analysis.

Longitudinal mixed modelling

Prior to undertaking longitudinal mixed modelling, we need to check the appropriateness of the default values for modelling parameters that are stored in X. These include the number of model iterations, and any custom control parameters and priors (by default, empty lists).

procureSlot(X, "b_SpecificParameters@iters_1L_int")
#> [1] 4000

In many cases there will be no need to specify any custom control parameters or priors and using the defaults may speed up execution.

procureSlot(X, "b_SpecificParameters@control_ls")
#> [[1]]
#> list()

procureSlot(X,"b_SpecificParameters@prior_ls")
#> [[1]]
#> list()

However, in this example using the default control parameters would result in warning messages suggesting a change to the adapt_delta control value (default = 0.8). Modifying the adapt_delta control parameter value can address this issue.

X <- renewSlot(X, "b_SpecificParameters@control_ls", new_val_xx = list(adapt_delta = 0.99))

X <- investigate(X, consent_1L_chr = consent_1L_chr)

class(X)
#> [1] "SpecificMixed"
#> attr(,"package")
#> [1] "specific"

The last call to investigate function wrote the models it tests to a sub-directory of the output directory along with plots for each model.

Create shareable outputs

The model objects created by the preceding analysis are not suitable for sharing as they contain duplicates of the source dataset. To create model objects that can be shared (where dataset copies are replaced with fake data) use the authorData method.

X <- authorData(X, consent_1L_chr = consent_1L_chr)

Purge dataset copies

For the purposes of efficient computation, multiple objects containing copies of the source dataset were saved to our output directory during the analysis process. We therefore need to delete all of these copies by supplying “purge_write” to the type_1L_chr argument of the author method.

X <- author(X, consent_1L_chr = consent_1L_chr, type_1L_chr = "purge_write")

A copy of the module X is available for download as the file eq5d_ttu_SpecificMixed.RDS from the “Documentation_0.0” release of the specific package.

Docs: Implement a utility mapping study

Fri, 20 Oct 2023 00:00:00 +0000

This below section renders a vignette article from the TTU library. You can use the following links to:

view the vignette on the library website (adds useful hyperlinks to code blocks)
view the source file from that article, and;
edit its contents (requires a GitHub account).

Note: This vignette uses fake data - it is for illustrative purposes only and should not be used to inform decision making. This vignette outlines the workflow for developing utility mapping models using longitudinal data. The workflow for developing utility mapping models is broadly similar, with some minor modifications. An example of developing models using cross-sectional data is available at https://doi.org/10.5281/zenodo.8098595 .

Motivation

Health services do not typically collect health utility data from their clients, which makes it more difficult to place an economic values on outcomes attained in these services. One strategy for addressing this gap is to use data from similar samples of patients that contain both health utility and the types of outcome measures that are collected in clinical services. The TTU package provides a toolkit for conducting and reporting a utility mapping (or Transfer to Utility) study.

Implementation

The TTU package contains modules of the ready4 youth mental health economic model that combine and extend model modules for:

labeling, validating and summarising youth mental health datasets (from the youthvars package);
scoring health utility (from the scorz package);
specifying and testing statistical models (from the specific package);
generating reproducible analysis reports (from the ready4show package); and
sharing data via online data repositories (from the ready4use package).

Additionally, TTU relies on two RMarkdown programs:

ttu_mdl_ctlg: Generate a Template Utility Mapping (Transfer to Utility) Model Catalogue (https://doi.org/10.5281/zenodo.5936870)
ttu_lng_ss: Create a Draft Scientific Manuscript For A Utility Mapping Study (https://doi.org/10.5281/zenodo.5976987)

Outputs generated by the TTU package are designed to be compatible with health economic models developed with the ready4 framework).

Workflow

Background and citation

The following workflow illustrates (using fake data) the same steps we used in a real world study, a summary of which is available at https://doi.org/10.1101/2021.07.07.21260129). Citation information for that study is:

@article {Hamilton2021.07.07.21260129,
    author = {Hamilton, Matthew P and Gao, Caroline X and Filia, Kate M and Menssink, Jana M and Sharmin, Sonia and Telford, Nic and Herrman, Helen and Hickie, Ian B and Mihalopoulos, Cathrine and Rickwood, Debra J and McGorry, Patrick D and Cotton, Sue M},
    title = {Predicting Quality Adjusted Life Years in young people attending primary mental health services},
    elocation-id = {2021.07.07.21260129},
    year = {2021},
    doi = {10.1101/2021.07.07.21260129},
    publisher = {Cold Spring Harbor Laboratory Press},
    URL = {https://www.medrxiv.org/content/early/2021/07/12/2021.07.07.21260129},
    eprint = {https://www.medrxiv.org/content/early/2021/07/12/2021.07.07.21260129.full.pdf},
    journal = {medRxiv}
}

The program applied in that study, which this workflow closely resembles is available at https://doi.org/10.5281/zenodo.6116077 and can be cited as follows:

@software{hamilton_matthew_2022_6212704,
  author       = {Hamilton, Matthew and
                  Gao, Caroline},
  title        = {{Complete study program to reproduce all steps from 
                   data ingest through to results dissemination for a
                   study to map mental health measures to AQoL-6D
                   health utility}},
  month        = feb,
  year         = 2022,
  note         = {{Matthew Hamilton and Caroline Gao  (2022). 
                   Complete study program to reproduce all steps from
                   data ingest through to results dissemination for a
                   study to map mental health measures to AQoL-6D
                   health utility. Zenodo.
                   https://doi.org/10.5281/zenodo.6116077. Version
                   0.0.9.3}},
  publisher    = {Zenodo},
  version      = {0.0.9.3},
  doi          = {10.5281/zenodo.6212704},
  url          = {https://doi.org/10.5281/zenodo.6212704}
}

Load required packages

We begin by loading our required packages.

library(ready4)
library(ready4show)
library(ready4use)
library(youthvars)
library(scorz)
library(TTU)

By default, methods associated with TTU modules will request your consent before writing files to your machine. This is the safest option. However, as there are many files that need to be written locally for this program to execute, you can overwrite this default by supplying the value “Y” to methods with a consent_1L_chr argument.

consent_1L_chr <- "" # Default value - asks for consent prior to writing each file.

Add dataset metadata

We use the Ready4useDyad and Ready4useRepos modules to retrieve and ingest and to then pair a dataset and its data dictionary.

A <- Ready4useDyad(ds_tb = Ready4useRepos(dv_nm_1L_chr = "fakes", dv_ds_nm_1L_chr = "https://doi.org/10.7910/DVN/HJXYKQ", dv_server_1L_chr = "dataverse.harvard.edu") %>%
                     ingest(fls_to_ingest_chr = c("ymh_clinical_tb"), metadata_1L_lgl = F) %>% youthvars::transform_raw_ds_for_analysis(),
                   dictionary_r3 = Ready4useRepos(dv_nm_1L_chr = "TTU", dv_ds_nm_1L_chr = "https://doi.org/10.7910/DVN/DKDIB0", dv_server_1L_chr = "dataverse.harvard.edu") %>%
                     ingest(fls_to_ingest_chr = c("dictionary_r3"), metadata_1L_lgl = F)) %>%
  renew(type_1L_chr = "label")

We use the YouthvarsSeries module to supply metadata about our longitudinal dataset vignette.

A <- YouthvarsSeries(a_Ready4useDyad = A, id_var_nm_1L_chr = "fkClientID", timepoint_var_nm_1L_chr = "round",
                     timepoint_vals_chr = levels(procureSlot(A, "ds_tb")$round))

Score health utility

We next use the ScorzAqol6Adol module to score adolescent AQoL-6D health utility.

A <- TTUProject(a_ScorzProfile = ScorzAqol6Adol(a_YouthvarsProfile = A))
A <- renew(A, what_1L_chr = "utility") 
#> Joining with `by = join_by(fkClientID, match_var_chr)`

Evaluate candidate models

Over the next few steps we will use modules from the specific package to specify and assess a number of candidate utility mapping models.

Specify modelling parameters

We begin by specifying the parameters we will use in our modelling project. The initial step is to ensure the fields in A for storing parameter values are internally consistent with the data we have entered in the previous steps.

A <- renew(A, what_1L_chr = "parameters")

We next ingest a lookup table of metadata about the variables we plan to explore as candidate predictors. In this case, we are sourcing the lookup table from an online data repository.

A <- renew(A, "use_renew_mthd", fl_nm_1L_chr = "predictors_r3", type_1L_chr = "predictors_lup", 
           y_Ready4useRepos = Ready4useRepos(dv_nm_1L_chr = "TTU", dv_ds_nm_1L_chr = "https://doi.org/10.7910/DVN/DKDIB0", 
                                             dv_server_1L_chr = "dataverse.harvard.edu"),
           what_1L_chr = "parameters")

We can inspect the metadata on candidate predictors that we have just ingested.

exhibit(A, scroll_box_args_ls = list(width = "100%"))

We add additional metadata about variables in our dataset that will be used in exploratory modelling.

A <- renew(A, c(0.03,1), type_1L_chr = "range", what_1L_chr = "parameters") %>%
  renew(c("BADS","GAD7", "K6", "OASIS", "PHQ9", "SCARED"),
        type_1L_chr = "predictors_vars", what_1L_chr = "parameters") %>%
  renew(c("d_sex_birth_s", "d_age",  "d_sexual_ori_s", "d_studying_working", "c_p_diag_s", "c_clinical_staging_s", "SOFAS"),     
        type_1L_chr = "covariates", what_1L_chr = "parameters") %>%
  renew(c("d_age","Gender","d_relation_s", "d_sexual_ori_s" ,"Region", "d_studying_working", "c_p_diag_s", "c_clinical_staging_s","SOFAS"), 
        type_1L_chr = "descriptives", what_1L_chr = "parameters") %>%
  renew("d_interview_date", type_1L_chr = "temporal", what_1L_chr = "parameters")

We record that the data we are working with is fake (this step can be skipped if working with real data).

A <- renew(A, T, type_1L_chr = "is_fake", what_1L_chr = "parameters")

We update A for internal consistency with the values we have previously supplied and create a local workspace to which output files will be written.

A <- renew(A, consent_1L_chr = consent_1L_chr, paths_chr = tempdir(), what_1L_chr = "project")

We now generate tables and charts that describe our dataset. These are saved in a sub-directory of our output data directory, and are available for download. One of the plots is also reproduced here.

A <- author(A, consent_1L_chr = consent_1L_chr, digits_1L_int = 3L, what_1L_chr = "descriptives")

We next compare the performance of different model types. We perform this step using the investigate method. This is the first of several times that we use this method. Each time the method is called A is updated to that the next time the method is called, a different algorithm will be used. The sequence of calls to investigate is therefore important (it should be in the same order as outlined in this example and you should not attempt to repeat a call to investigate to redo a prior step).

A <- investigate(A, consent_1L_chr = consent_1L_chr, depnt_var_max_val_1L_dbl = 0.9999, session_ls = sessionInfo())

The outputs of the previous command are saved into a sub-directory of our output directory. An example of this output is available for download). Once we inspect this output, we can then specify the preferred model types to use from this point onwards.

A <- renew(A, c("GLM_GSN_LOG", "OLS_CLL"), type_1L_chr = "models", what_1L_chr = "results")

Next we assess multiple versions of our preferred model type - one single predictor model for each of our candidate predictors and the same models with candidate covariates added.

A <- investigate(A, consent_1L_chr = consent_1L_chr)

The previous step saved output into a sub-directory of our output directory. Example output is available for download: (single predictor comparisons) and multivariate model comparisons. After reviewing this output, we can specify the covariates we wish to add to the models we will assess from this point forward.

A <- renew(A, "SOFAS", type_1L_chr = "covariates", what_1L_chr = "results")

We can now assess the multivariate models.

A <- investigate(A, consent_1L_chr = consent_1L_chr)

As a result of the previous step, more model objects and plot files have been saved to a sub-directory of our output directory. Examples of this output are available for download here and here. Once we inspect this output we can reformulate the models we finalised in the previous step so that they are suitable for modelling longitudinal change. For our primary analysis, we use a mixed model formulation of the models that we previously selected. A series of large model files are written to the local output data directory.

A <- investigate(A, consent_1L_chr = consent_1L_chr)

For our secondary analyses, we specify alternative combinations of predictors and covariates.

A <- investigate(A, consent_1L_chr = consent_1L_chr,
                 scndry_anlys_params_ls = make_scndry_anlys_params(candidate_predrs_chr = c("SOFAS"),
                                                                   candidate_covar_nms_chr = c("d_sex_birth_s", "d_age", "d_sexual_ori_s", "d_studying_working"),
                                                                   prefd_covars_chr = NA_character_) %>%
                   make_scndry_anlys_params(candidate_predrs_chr = c("SCARED","OASIS","GAD7"),
                                            candidate_covar_nms_chr = c("PHQ9", "SOFAS", "d_sex_birth_s", "d_age", "d_sexual_ori_s", "d_studying_working"),
                                            prefd_covars_chr = "PHQ9"))

Report findings

Create shareable models

The model objects created and saved in our working directory by the preceding steps are not suitable for public dissemination. They are both too large in file size and, more importantly, include copies of our source dataset. We can overcome these limitations by creating shareable versions of the models. Two types of shareable version are created - copies of the original model objects in which fake data overwrites the original source data and summary tables of model coefficients.

A <- author(A, consent_1L_chr = consent_1L_chr, what_1L_chr = "models")

Specify study reporting metadata

We update A so that we can begin use it to render and share reports.

A <- renew(A, what_1L_chr = "reporting")

We add metadata relevant to the reports that we will be generating to these fields. Note that the data we supply to the Ready4useRepos object below must relate to a repository to which we have write permissions (otherwise subsequent steps will fail).

A <- renew(A, ready4show::authors_tb, type_1L_chr = "authors", what_1L_chr = "reporting") %>%
  renew(ready4show::institutes_tb, type_1L_chr = "institutes", what_1L_chr = "reporting") %>%
  renew(c(3L,3L), type_1L_chr = "digits", what_1L_chr = "reporting") %>%
  renew(c("PDF","PDF"), type_1L_chr = "formats", what_1L_chr = "reporting") %>%
  renew("A hypothetical utility mapping study using fake data", type_1L_chr = "title", what_1L_chr = "reporting") %>%
  renew(renew(ready4show_correspondences(), old_nms_chr = c("PHQ9", "GAD7"), new_nms_chr = c("PHQ-9", "GAD-7")), type_1L_chr = "changes", what_1L_chr = "reporting") %>%
  renew(Ready4useRepos(dv_nm_1L_chr = "fakes", dv_ds_nm_1L_chr = "https://doi.org/10.7910/DVN/D74QMP", dv_server_1L_chr = "dataverse.harvard.edu"), type_1L_chr = "repos", what_1L_chr = "reporting")

Author model catalogues

We download a program for generating a catalogue of models and use it to summarising the models created under each study analysis (one primary and two secondary). The catalogues are saved locally.

A <- author(A, consent_1L_chr = consent_1L_chr, download_tmpl_1L_lgl = T, what_1L_chr = "catalogue")

Author manuscript

We add some content about the manuscript we wish to author.

A <- renew(A, "Quality Adjusted Life Years (QALYs) are often used in economic evaluations, yet utility weights for deriving them are rarely directly measured in mental health services.", 
           type_1L_chr = "background", what_1L_chr = "reporting") %>%
  renew("None declared", type_1L_chr = "conflicts", what_1L_chr = "reporting") %>%
  renew("Nothing should be concluded from this study as it is purely hypothetical.", type_1L_chr = "conclusion", what_1L_chr = "reporting") %>%
  renew("The study was reviewed and granted approval by no-one." , type_1L_chr = "ethics", what_1L_chr = "reporting") %>%
  renew("The study was funded by no-one.", type_1L_chr = "funding", what_1L_chr = "reporting") %>%
  renew("three months", type_1L_chr = "interval", what_1L_chr = "reporting") %>%
  renew(c("anxiety", "AQoL","depression", "psychological distress", "QALYs", "utility mapping"), type_1L_chr = "keywords", what_1L_chr = "reporting") %>%
  renew("The study sample is fake data.", type_1L_chr = "sample", what_1L_chr = "reporting")

We create a brief summary of results that can be interpreted by the program that authors the manuscript.

A <- renew(A, c("AQoL-6D", "Adolescent AQoL Six Dimension"), type_1L_chr = "naming", what_1L_chr = "reporting")

A <- renew(A, "use_renew_mthd", type_1L_chr = "abstract", what_1L_chr = "reporting")

We create and save the plots that will be used in the manuscript.

A <- author(A, consent_1L_chr = consent_1L_chr, what_1L_chr = "plots")

We download a program for generating a template manuscript and run it to author a first draft of the manuscript.

A <- author(A, consent_1L_chr = consent_1L_chr, download_tmpl_1L_lgl = T, what_1L_chr = "manuscript")

We can copy the RMarkdown files that created the template manuscript to a new directory (called “Manuscript_Submission”) so that we can then manually edit those files to produce a manuscript that we can submit for publication.

A <- author(A, consent_1L_chr = consent_1L_chr, type_1L_chr = "copy", what_1L_chr = "manuscript")

At this point in the workflow, additional steps are required to adapt / author the manuscript that will be submitted for publication. However, in this example we are going to skip that step and keep working with the unedited template manuscript. If we had a finalised manuscript authoring program stored online, we could now specify the repository from which the program can be retrieved.

# Not run
# A <- renew(A, c("URL of GitHub repository with", "Program version number"), type_1L_chr = "template-manuscript", what_1L_chr = "reporting")

We can now configure the output to be generated by the manuscript authoring program. The below commands will specify a Microsoft Word format manuscript and a PDF technical appendix. Unlike the template manuscript, the figures and tables will be positioned after (and not within) the main body of the manuscript. Note that the Word version of the manuscript generated by these values will require some minor formatting edits (principally to the display of tables and numbering of sections).

A <- renew(A, F, type_1L_chr = "figures-body", what_1L_chr = "reporting") %>%
  renew(F, type_1L_chr = "tables-body", what_1L_chr = "reporting") %>%
  renew(c("Word","PDF"), type_1L_chr = "formats", what_1L_chr = "reporting")

Once any edits to the RMarkdown files for creating the submission manuscript have been finalised, we can run the following command to author the manuscript. If we are using a custom manuscript authoring program downloaded from an online repository the download_tmpl_1L_lgl argument will need to be set to T.

A <- author(A, consent_1L_chr = consent_1L_chr, download_tmpl_1L_lgl = F, type_1L_chr="submission", what_1L_chr = "manuscript")

We can now generate the Supplementary Information for the submission manuscript.

A <- author(A, consent_1L_chr = consent_1L_chr, supplement_fl_nm_1L_chr = "TA_PDF", type_1L_chr="submission", what_1L_chr = "supplement")

We can now share non-confidential elements (ie no copies of individual records) of the outputs that we have created via our study online repository. To run this step you will need write permissions to the online repository. In the below step we are sharing model catalogues, details of the utility instrument, the shareable mapping models (designed to be used in conjunction with the youthu package), our manuscript files and our supplementary information. In most real world studies the manuscript would not be shared via an online repository - the what_chr argument would need to be ammended to reflect this.

A <- share(A, types_chr = c("auto", "submission"), what_chr = c("catalogue", "instrument" ,"manuscript", "models", "supplement"))

The dataset we created in the previous step is viewable here: https://dataverse.harvard.edu/dataset.xhtml?persistentId=doi:10.7910/DVN/D74QMP

Tidy workspace

The preceding steps saved multiple objects (mostly R model objects) that have embedded within them copies of the source dataset. To protect the confidentiality of these records we can now purge all such copies from our output data directory.

A <- author(A, what_1L_chr = "purge")

Docs: Find and deploy utility mapping models

Fri, 20 Oct 2023 00:00:00 +0000

This below section renders a vignette article from the youthu library. You can use the following links to:

view the vignette on the library website (adds useful hyperlinks to code blocks)
view the source file from that article, and;
edit its contents (requires a GitHub account).

library(youthu)

This vignette outlines a workflow for:

Searching, selecting and retrieving transfer to utility models;
Preparing a prediction dataset for use with a selected transfer to utility model; and
Applying the selected transfer to utility model to a prediction dataset to predict Quality Adjusted Life Years (QALYs).

The practical value of implementing such a workflow is discussed in the economic analysis vignette and a scientific manuscript. Note, this example uses fake data - it should should not be used to inform decision making.

Search, select and retrieve transfer to utility models

To identify datasets that contain transfer to utility models compatible with youthu (ie those developped with the TTU package), you can use the get_ttu_dv_dss function. The function searches specified dataverses (in the below example, the TTU dataverse) for datasets containing output from the TTU package.

ttu_dv_dss_tb <- get_ttu_dv_dss("TTU")

The ttu_dv_dss_tb table summarises some pertinent details about each dataset containing TTU models found by the preceding command. These details include a link to any scientific summary (the “Article” column) associated with a dataset.

Transfer to Utility Datasets
ID	Utility	Predictors	Article
1	aqol6dtotalw	BADS total score , GAD7 total score , K6 total score , OASIS total score , PHQ9 total score , SCARED total score, SOFAS total score

To identify models that predict a specified type of health utility from one or more of a specified subset of predictors, use:

mdls_lup <- get_mdls_lup(ttu_dv_dss_tb = ttu_dv_dss_tb,
                         utility_type_chr = "AQoL-6D",
                         mdl_predrs_in_ds_chr = c("PHQ9 total score",
                                                  "SOFAS total score"))

The preceding command will produce a lookup table with information that includes the catalogue names of models, the predictors used in each model and the analysis that generated each one.

Selected elements from Models Look-Up Table
Catalogue reference	Predictors	Analysis
PHQ9_1_GLM_GSN_LOG	PHQ9	Primary Analysis
PHQ9_1_OLS_CLL	PHQ9	Primary Analysis
PHQ9_SOFAS_1_GLM_GSN_LOG	PHQ9 , SOFAS	Primary Analysis
PHQ9_SOFAS_1_OLS_CLL	PHQ9 , SOFAS	Primary Analysis
OASIS_SOFAS_1_GLM_GSN_LOG	OASIS, SOFAS	Primary Analysis
OASIS_SOFAS_1_OLS_CLL	OASIS, SOFAS	Primary Analysis
BADS_SOFAS_1_GLM_GSN_LOG	BADS , SOFAS	Primary Analysis
BADS_SOFAS_1_OLS_CLL	BADS , SOFAS	Primary Analysis
K6_SOFAS_1_GLM_GSN_LOG	K6 , SOFAS	Primary Analysis
K6_SOFAS_1_OLS_CLL	K6 , SOFAS	Primary Analysis
SCARED_SOFAS_1_GLM_GSN_LOG	SCARED, SOFAS	Primary Analysis
SCARED_SOFAS_1_OLS_CLL	SCARED, SOFAS	Primary Analysis
GAD7_SOFAS_1_GLM_GSN_LOG	GAD7 , SOFAS	Primary Analysis
GAD7_SOFAS_1_OLS_CLL	GAD7 , SOFAS	Primary Analysis
SOFAS_1_GLM_GSN_LOG	SOFAS	Secondary Analysis A
SOFAS_1_OLS_CLL	SOFAS	Secondary Analysis A
OASIS_PHQ9_1_GLM_GSN_LOG	OASIS, PHQ9	Secondary Analysis B
OASIS_PHQ9_1_OLS_CLL	OASIS, PHQ9	Secondary Analysis B
GAD7_PHQ9_1_GLM_GSN_LOG	GAD7, PHQ9	Secondary Analysis B
GAD7_PHQ9_1_OLS_CLL	GAD7, PHQ9	Secondary Analysis B
SCARED_PHQ9_1_GLM_GSN_LOG	SCARED, PHQ9	Secondary Analysis B
SCARED_PHQ9_1_OLS_CLL	SCARED, PHQ9	Secondary Analysis B

To review the summary information about the predictive performance of a specific model, use:

get_dv_mdl_smrys(mdls_lup,
                 mdl_nms_chr = "PHQ9_SOFAS_1_OLS_CLL")
#> $PHQ9_SOFAS_1_OLS_CLL
#>        Parameter Estimate    SE          95% CI
#> 1 SD (Intercept)    0.348 0.017   0.312 , 0.382
#> 2      Intercept    0.428 0.129   0.174 , 0.686
#> 3  PHQ9 baseline   -9.115 0.249 -9.601 , -8.618
#> 4    PHQ9 change   -7.331 0.339 -8.007 , -6.665
#> 5 SOFAS baseline    0.960 0.172   0.616 , 1.292
#> 6   SOFAS change    1.146 0.235   0.674 , 1.607
#> 7             R2    0.767 0.012   0.743 , 0.788
#> 8           RMSE    0.925 0.004   0.922 , 0.928
#> 9          Sigma    0.406 0.012   0.384 , 0.429

More information about a selected model can be found in the online model catalogue, the link to which can be obtained with the following command:

get_mdl_ctlg_url(mdls_lup,
                 mdl_nm_1L_chr = "PHQ9_SOFAS_1_OLS_CLL")

[1] “https://dataverse.harvard.edu/api/access/datafile/6484935”

Prepare a prediction dataset for use with a selected transfer to utility model

Import data

You can now import and inspect the dataset you plan on using for prediction. In the below example we use fake data.

data_tb <- make_fake_ds_one()

Illustrative example of a prediction dataset
UID	Timepoint	Date	PHQ_total	SOFAS_total
Participant_1	Baseline	2022-05-22	7	69
Participant_10	Baseline	2022-04-07	17	60
Participant_10	Follow-up	2022-06-22	17	64
Participant_100	Baseline	2022-07-29	0	76
Participant_1000	Baseline	2022-02-10	0	71
Participant_1000	Follow-up	2022-05-05	0	71

Confirm dataset can be used as a prediction dataset

The prediction dataset must contain variables that correspond to all the predictors of the model you intend to apply. The allowable range and required class of each predictor variable are described in the min_val_dbl, max_val_dbl and class_chr columns of the model predictors lookup table, which can be accessed with a call to the get_predictors_lup function.

predictors_lup <- get_predictors_lup(mdls_lup = mdls_lup,
                                     mdl_nm_1L_chr = "PHQ9_SOFAS_1_OLS_CLL")

Model predictors lookup table
short_name_chr	long_name_chr	min_val_dbl	max_val_dbl	class_chr	increment_dbl	class_fn_chr	mdl_scaling_dbl	covariate_lgl
PHQ9	PHQ9 total score	0	27	integer	1	youthvars::youthvars_phq9	0.01	FALSE
SOFAS	SOFAS total score	0	100	integer	1	youthvars::youthvars_sofas	0.01	TRUE

The prediction dataset must also include both a unique client identifier variable and a measurement time-point identifier variable (which must be a factor with two levels). The dataset also needs to be in long format (ie where measures at different time-points for the same individual are stacked on top of each other in separate rows). We can confirm these conditions hold by creating a dataset metadata object using the make_predn_metadata_ls function. In creating the metadata object, the function checks that the dataset can be used in conjunction with the model specified at the mdl_nm_1L_chr argument. If the prediction dataset uses different variable names for the predictors to those specified in the predictors_lup lookup table, a named vector detailing the correspondence between the two sets of variable names needs to be passed to the predr_vars_nms_chr argument. Finally, if you wish to specify a preferred variable name to use for the predicted utility values when applying the model, you can do this by passing this name to the utl_var_nm_1L_chr argument.

predn_ds_ls <- make_predn_metadata_ls(data_tb,
                                      id_var_nm_1L_chr = "UID",
                                      msrmnt_date_var_nm_1L_chr = "Date",
                                      predr_vars_nms_chr = c(PHQ9 = "PHQ_total",SOFAS = "SOFAS_total"),
                                      round_var_nm_1L_chr = "Timepoint",
                                      round_bl_val_1L_chr = "Baseline",
                                      utl_var_nm_1L_chr = "AQoL6D_HU",
                                      mdls_lup = mdls_lup,
                                      mdl_nm_1L_chr = "PHQ9_SOFAS_1_OLS_CLL")

Apply the selected transfer to utility model to a prediction dataset to predict Quality Adjusted Life Years (QALYs)

Predict health utility at baseline and follow-up timepoints

To generate utility predictions we use the add_utl_predn function. The function needs to be supplied with the prediction dataset (the value passed to argument data_tb) and the validated prediction metadata object we created in the previous step.

data_tb <- add_utl_predn(data_tb,
                         predn_ds_ls = predn_ds_ls)
#> Joining with `by = join_by(UID, Timepoint)`

By default the add_utl_predn function samples model parameter values based on a table of model coefficients when making predictions and constrains predictions to an allowed range. You can override these defaults by adding additional arguments new_data_is_1L_chr = "Predicted" (which uses mean parameter values), force_min_max_1L_lgl = F (removes range constraint) and (if the source dataset makes available downloadable model objects) make_from_tbl_1L_lgl = F. These settings will produce different predictions. It is strongly recommended that you consult the model catalogue (see above) to understand how such decisions may affect the validity of the predicted values that will be generated.

Prediction dataset with predicted utilities
UID	Timepoint	Date	PHQ_total	SOFAS_total	AQoL6D_HU
Participant_1	Baseline	2022-05-22	7	69	0.9080468
Participant_10	Baseline	2022-04-07	17	60	0.5533808
Participant_10	Follow-up	2022-06-22	17	64	0.4006010
Participant_100	Baseline	2022-07-29	0	76	0.6809903
Participant_1000	Baseline	2022-02-10	0	71	0.9877882
Participant_1000	Follow-up	2022-05-05	0	71	0.9602037

Our health utility predictions are now available for use and are summarised below.

summary(data_tb$AQoL6D_HU)
#>    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
#> 0.06646 0.42781 0.63403 0.62335 0.83351 1.00000

Calculate QALYs

The last step is to calculate Quality Adjusted Life Years, using a method assuming a linear rate of change between timepoints.

data_tb <- data_tb %>% add_qalys_to_ds(predn_ds_ls = predn_ds_ls,
                                       include_predrs_1L_lgl = F,
                                       reshape_1L_lgl = F)

Prediction dataset with QALYs
UID	Timepoint	Date	PHQ_total	SOFAS_total	AQoL6D_HU	AQoL6D_HU_change_dbl	duration_prd	qalys_dbl
Participant_1	Baseline	2022-05-22	7	69	0.9080468	0.0000000	0S	0.0000000
Participant_10	Baseline	2022-04-07	17	60	0.5533808	0.0000000	0S	0.0000000
Participant_10	Follow-up	2022-06-22	17	64	0.4006010	-0.1527798	76d 0H 0M 0S	0.0992507
Participant_100	Baseline	2022-07-29	0	76	0.6809903	0.0000000	0S	0.0000000
Participant_1000	Baseline	2022-02-10	0	71	0.9877882	0.0000000	0S	0.0000000
Participant_1000	Follow-up	2022-05-05	0	71	0.9602037	-0.0275845	84d 0H 0M 0S	0.2239991

Docs: Use utility mapping algorithms to help implement cost-utility analyses

Fri, 20 Oct 2023 00:00:00 +0000

This below section renders a vignette article from the youthu library. You can use the following links to:

view the vignette on the library website (adds useful hyperlinks to code blocks)
view the source file from that article, and;
edit its contents (requires a GitHub account).

library(youthu)
set.seed(1234)

This vignette illustrates the rationale for and practical decision-making utility of youthu’s QALYs prediction workflow. Note, this example is illustrated with fake data and should not be used to inform decision-making.

Motivation

The main motivation behind the youthu package is to extend the types of economic analysis that can be undertaken with both single group (e.g. pilot study, health service records) and matched groups (e.g. trial) longitudinal datasets that do not include measures of health utility. This article focuses on its application to matched group datasets.

Example dataset

First, we must first import our data. In this example we will use a fake dataset.

ds_tb <- make_fake_ds_two()
#> Joining with `by = join_by(fkClientID, study_arm_chr)`

Our dataset includes 268 matched comparisons, with each comparison containing baseline and follow-up records for one intervention arm participant and one control arm participant. The first few records are as follows.

First few records from input dataset
fkClientID	round	date_psx	duration_prd	PHQ9	SOFAS	costs_dbl	study_arm_chr	match_idx_int
Participant_20	Baseline	2023-03-15	0S	16	41	301.1868	Intervention	1
Participant_593	Baseline	2023-01-20	0S	19	43	259.3190	Control	1
Participant_593	Follow-up	2023-07-14	175d 0H 0M 0S	16	65	1290.4220	Control	1
Participant_20	Follow-up	2023-09-09	178d 0H 0M 0S	15	74	1787.4242	Intervention	1
Participant_259	Baseline	2023-05-10	0S	19	39	311.0018	Control	2
Participant_962	Baseline	2023-06-22	0S	10	45	276.2181	Intervention	2

This dataset contains features that make it possible to use in conjunction with youthu’s economic analysis functions. These requirements are described in the vignette about finding and using models compatible models to predict QALYs;

The dataset also contains a cost variable, which is a requirement for most, though not all, of the economic analyses that can be undertaken with youthu.

Limitations of datasets without measures of health utility

A notable omission from the dataset is any measure of utility. This omission means that, in the absence of using mapping algorithms such as those included with youthu, the most feasible types of economic evaluation to apply to this dataset would likely be cost-consequence analysis (where a synopsis of the differences in a range of measures are presented alongside cost differences) and cost-effectiveness analysis (where a summary statistic - the incremental cost-effectiveness ratio or ICER - is calculated by dividing differences in costs by differences in a single outcome measure).

These types of economic analyses can be relatively simple to interpret if either the intervention or control arm is simultaneously cheaper and more effective across all included outcome measures. However, these conditions don’t hold in our sample data.

summary((ds_tb %>% dplyr::filter(study_arm_chr == "Control" & round == "Baseline"))[5:6])
#>       PHQ9          SOFAS      
#>  Min.   : 0.0   Min.   :39.00  
#>  1st Qu.: 7.0   1st Qu.:60.00  
#>  Median :12.0   Median :66.00  
#>  Mean   :10.9   Mean   :66.13  
#>  3rd Qu.:15.0   3rd Qu.:72.00  
#>  Max.   :19.0   Max.   :89.00

summary((ds_tb %>% dplyr::filter(study_arm_chr == "Control" & round == "Follow-up"))[5:7])
#>       PHQ9            SOFAS         costs_dbl     
#>  Min.   : 0.000   Min.   :39.00   Min.   : 889.9  
#>  1st Qu.: 4.000   1st Qu.:64.00   1st Qu.:1321.1  
#>  Median : 8.000   Median :71.00   Median :1486.7  
#>  Mean   : 8.493   Mean   :70.65   Mean   :1489.0  
#>  3rd Qu.:13.000   3rd Qu.:77.00   3rd Qu.:1627.0  
#>  Max.   :27.000   Max.   :98.00   Max.   :2216.5

summary((ds_tb %>% dplyr::filter(study_arm_chr == "Intervention" & round == "Baseline"))[5:6])
#>       PHQ9           SOFAS      
#>  Min.   : 0.00   Min.   :36.00  
#>  1st Qu.: 7.00   1st Qu.:61.00  
#>  Median :11.00   Median :67.00  
#>  Mean   :10.81   Mean   :66.74  
#>  3rd Qu.:15.00   3rd Qu.:72.25  
#>  Max.   :19.00   Max.   :88.00

summary((ds_tb %>% dplyr::filter(study_arm_chr == "Intervention" & round == "Follow-up"))[5:7])
#>       PHQ9            SOFAS      costs_dbl     
#>  Min.   : 0.000   Min.   :40   Min.   : 923.4  
#>  1st Qu.: 2.000   1st Qu.:60   1st Qu.:1625.6  
#>  Median : 6.500   Median :68   Median :1777.3  
#>  Mean   : 6.851   Mean   :68   Mean   :1807.8  
#>  3rd Qu.:11.000   3rd Qu.:77   3rd Qu.:1996.0  
#>  Max.   :25.000   Max.   :93   Max.   :2872.7

The pattern of results summarised above create some significant barriers to meaningfully interpreting economic evaluations that are based on cost-consequence or cost-effectiveness analysis:

A cost-effectiveness analysis in which change in PHQ-9 was the benefit measure would be difficult to interpret as the Intervention arm is both more effective and more costly, which begs the question is it worth paying the extra dollars for this improvement? Also - would a judgment of cost-effectiveness remain the same if the study had measured a slightly different incremental benefit or recorded change over a longer or shorter time horizon? It is likely that there is no commonly used value for money benchmark for improvements measured in PHQ-9, nor is there any time weighting associated with the measure. Furthermore, if the potential funding for the intervention is from a budget that is allocated to non-depressive illnesses (e.g. physical health), results from a cost-effectiveness analysis using PHQ-9 as its benefit measure are not readily comparable with economic evaluations of interventions from other illness groups using different benefit measures that are potentially competing for the same scarce funding.
A cost consequence analyses that summarised the differences in costs with the differences in changes in PHQ-9 and SOFAS score would be difficult to interpret because while the intervention is more effective than control for improvements measured on PHQ-9 (where lower scores are better), the control group is superior if benefits are based on functioning improvements as measured by SOFAS scores (where higher scores are better). The lack of any formal weighting for how to trade off clinical symptoms and functioning means that interpretation of this analysis will be highly subjective and likely to change across potential decision makers.

These types of short-comings can be significantly addressed by undertaking cost-utility analyses (CUAs) as:

they use a measure of benefit - the Quality Adjusted Life Year (QALY) - that captures multiple domains of health, weighted by time and population preferences in a single index measure that can be applied across health conditions;
there are published benchmark willingness to pay values for QALYs that are routinely used by decision makers in many countries to make ICER statistics readily interpretable in the context of health budget allocation.

The rest of this article demonstrates how youthu functions can be used to undertake CUA based analyses on the type of data we have just profiled.

Using youthu in a cost-utility analysis workflow

Predict adolescent AQoL-6D health utility

Our first step is to identify which youthu models we will use to predict adolescent AQoL-6D and apply these models to our data. This step was explained in more detail in another vignette article about finding and using transfer to utility models, so will be dealt with briefly here.

First we make sure that our dataset can be used as a prediction dataset in conjunction with the model we intend using.

predn_ds_ls <- make_predn_metadata_ls(ds_tb,
                                      cmprsn_groups_chr = c("Intervention", "Control"),
                                      cmprsn_var_nm_1L_chr = "study_arm_chr",
                                      costs_var_nm_1L_chr = "costs_dbl",
                                      id_var_nm_1L_chr = "fkClientID",
                                      msrmnt_date_var_nm_1L_chr = "date_psx",
                                      round_var_nm_1L_chr = "round",
                                      round_bl_val_1L_chr = "Baseline",
                                      utl_var_nm_1L_chr = "AQoL6D_HU",
                                      mdls_lup = get_mdls_lup(utility_type_chr = "AQoL-6D",
                                                              mdl_predrs_in_ds_chr = c("PHQ9 total score",
                                                                                       "SOFAS total score"),
                                                              ttu_dv_nms_chr = "TTU"),
                                      mdl_nm_1L_chr =  "PHQ9_SOFAS_1_OLS_CLL")

We now use our preferred model to predict health utility from the measures in our dataset.

ds_tb <- add_utl_predn(ds_tb,
                       predn_ds_ls = predn_ds_ls) %>%
  dplyr::select(fkClientID, round, study_arm_chr, date_psx, duration_prd, dplyr::everything())
#> Joining with `by = join_by(fkClientID, round)`

Calculate QALYs

Next we combine the health utility data with the interval between measurement data to calculate QALYs and add them to the dataset.

ds_tb  <- ds_tb %>% add_qalys_to_ds(predn_ds_ls = predn_ds_ls,
                                    include_predrs_1L_lgl = T,
                                    reshape_1L_lgl = T)

First few records from updated dataset with QALYs
fkClientID	study_arm_chr	match_idx_int	date_psx_Baseline	date_psx_Follow-up	duration_prd_Baseline	duration_prd_Follow-up	costs_dbl_Baseline	costs_dbl_Follow-up	PHQ9_Baseline	PHQ9_Follow-up	SOFAS_Baseline	SOFAS_Follow-up	AQoL6D_HU_Baseline	AQoL6D_HU_Follow-up	PHQ9_change_dbl_Baseline	PHQ9_change_dbl_Follow-up	SOFAS_change_dbl_Baseline	SOFAS_change_dbl_Follow-up	AQoL6D_HU_change_dbl_Baseline	AQoL6D_HU_change_dbl_Follow-up	qalys_dbl_Baseline	qalys_dbl_Follow-up
Participant_10	Control	243	2022-12-29	2023-06-24	0S	177d 0H 0M 0S	647.9386	1696.235	8	10	61	64	0.7597988	0.6079774	0	2	0	3	0	-0.1518214	0	0.3314119
Participant_1000	Control	191	2023-02-24	2023-08-27	0S	184d 0H 0M 0S	428.9205	1619.037	4	2	63	82	0.8459579	0.7688131	0	-2	0	19	0	-0.0771448	0	0.4067322
Participant_1001	Intervention	230	2023-01-19	2023-07-17	0S	179d 0H 0M 0S	429.3703	1844.219	10	14	59	72	0.6138300	0.8607305	0	4	0	13	0	0.2469005	0	0.3613228
Participant_1003	Intervention	115	2023-02-17	2023-08-18	0S	182d 0H 0M 0S	395.1637	1537.365	9	0	71	81	0.5808015	0.9315788	0	-9	0	10	0	0.3507773	0	0.3768011
Participant_1005	Intervention	183	2023-05-21	2023-11-23	0S	186d 0H 0M 0S	402.9910	1826.511	17	0	78	88	0.5460607	0.9593811	0	-17	0	10	0	0.4133204	0	0.3833158
Participant_1006	Intervention	219	2023-06-16	2023-12-12	0S	179d 0H 0M 0S	534.2285	2401.478	9	14	75	73	0.7239490	0.5885972	0	5	0	-2	0	-0.1353518	0	0.3216232

Analyse results

Now we can run the main economic analysis. This is implemented by the make_hlth_ec_smry function, which first bootstraps the dataset (implemented by the boot function from the boot package) before passing the mean values for costs and QALYs from each bootstrap sample to with bcea function of the BCEA package to calculate a range of health economic statistics. For this example we pass a value of 50,000 for the willingness to pay parameter, as this is the dollar amount commonly used in Australia as a benchmark for the value of a QALY.

Note, for this illustrative example we only request 1000 bootstrap iterations - in practice this number may be higher.

he_smry_ls <- ds_tb %>% make_hlth_ec_smry(predn_ds_ls = predn_ds_ls,
                                                 wtp_dbl = 50000,
                                                 bootstrap_iters_1L_int = 1000L)
#> Warning: There was 1 warning in `dplyr::summarise()`.
#> ℹ In argument: `dplyr::across(.fns = mean)`.
#> Caused by warning:
#> ! Using `across()` without supplying `.cols` was deprecated in dplyr 1.1.0.
#> ℹ Please supply `.cols` instead.

As part of the output of the make_hlth_ec_smry function is a BCEA object, we can use the BCEA package to produce a number of graphical summaries of economic results. One of the most important is the production of a cost-effectiveness plane. This plot highlights that, with an ICER of $-98,145.56, less than half of the bootstrapped iteration incremental cost and QALY pairs fall within the zone of cost-effectiveness (green). In fact, at the cost-effectiveness threshold we supplied, the results suggest there is a 8% probability that the intervention is cost-effective.

library(ggplot2)
BCEA::ceplane.plot(he_smry_ls$ce_res_ls, wtp =50000,    
                   area_color = "green",
                    graph = "ggplot2",
          theme = ggplot2::theme_light())
#> Warning: Duplicated aesthetics after name standardisation: colour

Docs: Develop health utility mapping algorithms

Thu, 05 Jan 2017 00:00:00 +0000

This below section embeds a PDF version of an R Markdown program. The following alternative options may provide improved viewing experience, more contextual information and access to more useful code formats:

Docs: Predict health utility

Thu, 05 Jan 2017 00:00:00 +0000

Docs: Make a catalogue of utility mapping models

Thu, 05 Jan 2017 00:00:00 +0000

This below section reproduces the README file of an R Markdown sub-routine. The following alternative options may provide more contextual information and access to more useful code formats:

view examples of the catalogues produced by this subroutine in a study dataset (the names of the relevant files all begin with “AAA_TTU_MDL_CTG”);
view the README along with the current release of its R Markdown code (useful if you plan to run the code); and
view the README along with the current development version of its R Markdown code (useful if you wish to copy or edit the code)

ttu_mdl_ctlg

R Markdown subroutine reporting template for creating utility mapping (transfer to utility) model catalogues. This template should be used in conjunction with the TTU R package.

Docs: Author a draft scientific manuscript for a utility mapping study

Thu, 05 Jan 2017 00:00:00 +0000

This below section reproduces the README file of an R Markdown sub-routine. The following alternative options may provide more contextual information and access to more useful code formats:

Create a Draft Scientific Manuscript For A Utility Mapping Study

This sub-routine program extends the R package TTU by providing a toolkit for automatically authoring a first draft of a scientific manuscript from results generated by TTU modules.

The program is intended for use and as the last component of TTU’s reporting workflow for utility mapping modelling projects. An example of this workflow is available at: https://doi.org/10.5281/zenodo.6116077 . This program generalises a program that produced the manuscript for a real world study (https://doi.org/10.1101/2021.07.07.21260129).

The program can produce manuscripts in PDF / LaTex (example - https://dataverse.harvard.edu/api/access/datafile/4957407) and Word (example - https://dataverse.harvard.edu/api/access/datafile/4957416). It should be noted that the Word output requires some manual editing to adapt section numbering, modify table headers and resize tables to page boundaries.

Suggested citation (bibTeX):

@software{hamilton_matthew_2022_6931146, author = {Hamilton, Matthew and Gao, Caroline}, title = {{ttu_lng_ss: Create a Draft Scientific Manuscript For A Utility Mapping Study}}, month = jun, year = 2023, note = {{Matthew Hamilton and Caroline Gao (2022). ttu_lng_ss: Create a Draft Scientific Manuscript For A Utility Mapping Study. Zenodo. https://doi.org/10.5281/zenodo.5976987. Version 0.9.0.0}}, publisher = {Zenodo}, version = {0.9.0.0}, doi = {10.5281/zenodo.5976987}, url = {https://doi.org/10.5281/zenodo.5976987} }

ready4 – Use - utility mapping

Docs: Examples

Docs: Model health utility

Docs: Explore candidate utility mapping models

Set consent policy

Import data

Inspect data

Specify parameters

Dependent variable

Candidate predictors

Covariates

Descriptive variables

Temporal variables

Candidate models

Other parameters

Model testing

Set-up workspace

Descriptives

Model comparisons

Use most preferred model to compare all candidate predictors

Test preferred model with preferred covariates for each candidate predictor

Apply preferred model types and predictors to longitudinal data

Longitudinal mixed modelling

Create shareable outputs

Purge dataset copies

Docs: Implement a utility mapping study

Motivation

Implementation

Workflow

Background and citation

Load required packages

Set consent policy

Add dataset metadata

Score health utility

Evaluate candidate models

Specify modelling parameters

Report findings

Create shareable models

Specify study reporting metadata

Author model catalogues

Author manuscript

Share outputs

Tidy workspace

Docs: Find and deploy utility mapping models

Search, select and retrieve transfer to utility models

Prepare a prediction dataset for use with a selected transfer to utility model

Import data

Confirm dataset can be used as a prediction dataset

Apply the selected transfer to utility model to a prediction dataset to predict Quality Adjusted Life Years (QALYs)

Predict health utility at baseline and follow-up timepoints

Calculate QALYs

Docs: Use utility mapping algorithms to help implement cost-utility analyses

Motivation

Example dataset

Limitations of datasets without measures of health utility

Using youthu in a cost-utility analysis workflow

Predict adolescent AQoL-6D health utility

Calculate QALYs

Analyse results

Docs: Develop health utility mapping algorithms

Docs: Predict health utility

Docs: Make a catalogue of utility mapping models

ttu_mdl_ctlg

Docs: Author a draft scientific manuscript for a utility mapping study

Create a Draft Scientific Manuscript For A Utility Mapping Study