ModelValidation {iCARE} | R Documentation

## Model Validation

### Description

This function is used to validate absolute risk models.

### Usage

    ModelValidation(study.data,
                    total.followup.validation = FALSE,
                    predicted.risk = NULL,
                    predicted.risk.interval = NULL,
                    linear.predictor = NULL,
                    iCARE.model.object =
                      list(model.formula = NULL,
                           model.cov.info = NULL,
                           model.snp.info = NULL,
                           model.log.RR = NULL,
                           model.ref.dataset = NULL,
                           model.ref.dataset.weights = NULL,
                           model.disease.incidence.rates = NULL,
                           model.competing.incidence.rates = NULL,
                           model.bin.fh.name = NA,
                           apply.cov.profile  = NULL,
                           apply.snp.profile = NULL,
                           n.imp = 5, use.c.code = 1,
                           return.lp = TRUE,
                           return.refs.risk = TRUE),
                    number.of.percentiles = 10,
                    reference.entry.age = NULL,
                    reference.exit.age = NULL,
                    predicted.risk.ref = NULL,
                    linear.predictor.ref = NULL,
                    linear.predictor.cutoffs = NULL,
                    dataset = "Example Dataset",
                    model.name = "Example Risk Prediction Model")

### Arguments

`study.data` | Data frame which includes the variables below. `observed.outcome`: 1 if disease has occurred by the end of followup, 0 if censored `study.entry.age`: age (in years) of entering the cohort `study.exit.age`: age (in years) of last followup visit `time.of.onset`: time (in years) of onset of disease; note that all subjects are disease free at the time of entry and for those who do not develop disease by end of followup it is Inf `sampling.weights`: for a case-control study nested within a cohort study, this is a vector of sampling weights for each subject, i.e., probability of inclusion into the sample
`total.followup.validation` | logical; TRUE if risk validation is performed over the total followup, for all other cases (e.g., 5 year or 10 year risk validation) it is FALSE
`predicted.risk` | vector of predicted risks; should be supplied if risk prediction is done by some method other than that implemented in `iCARE`; default is NULL
`predicted.risk.interval` | scalar or vector denoting the number of years after entering the study over which risk validation is desired (e.g., 5 for validating a model for 5 year risk) if `total.followup.validation = FALSE`; if `total.followup.validation = TRUE`, it can be set to NULL
`linear.predictor` | vector of risk scores for each subject, i.e. `x*beta`, where `x` is the vector of risk factors and `beta` is the vector of log relative risks; in the current version if both the arguments `predicted.risk` and `linear.predictor` are supplied the function will use the supplied estimates to perform model validation, otherwise the function will compute these estimates using the `computeAbsoluteRisk` function
`iCARE.model.object` | A named list containing the input arguments to the function `computeAbsoluteRisk`. The names in this list must match the argument names. See `computeAbsoluteRisk`
`number.of.percentiles` | the number of percentiles of the risk score that determines the number of strata over which the risk prediction model is to be validated, default = 10
`reference.entry.age` | age of entry to be specified for computing absolute risk of the reference population
`reference.exit.age` | age of exit to be specified for computing absolute risk of the reference population
`predicted.risk.ref` | predicted absolute risk in the reference population assuming the entry age to be as specified in `reference.entry.age` and exit age to be as specified in `reference.exit.age`
`linear.predictor.ref` | vector of risk scores for the reference population
`linear.predictor.cutoffs` | user specified cut-points for the linear predictor to define categories for absolute risk calibration and relative risk calibration
`dataset` | name and type of dataset to be displayed in the output, e.g., "PLCO Full Cohort" or "Full Cohort Simulation"
`model.name` | name of the model to be displayed in output, e.g., "Synthetic Model" or "Simulation Setting"

### Value

This function returns a list of the following objects:

- `Subject_Specific_Observed_Outcome`: observed outcome after adjusting the observed followup according to the risk prediction interval: 1 if disease has occurred by the end of followup, 0 if censored

- `Risk_Prediction_Interval`: Character object showing the interval of risk prediction (e.g., 5 years). If the risk prediction is over the total followup of the study, this reads "Observed Followup"

- `Adjusted.Followup`: followup time (in years) after adjusting the observed followup according to the risk prediction interval

- `Subject_Specific_Predicted_Absolute_Risk`: predicted absolute risk of disease for each subject

- `Reference_Absolute_Risk`: predicted absolute risk in the reference population

- `Subject_Specific_Risk_Score`: estimated risk score for each subject; the missing covariates are handled internally using the imputation in `iCARE`

- `Reference_Risk_Score`: risk score for the reference population

- `Population_Incidence_Rate`: age specific disease incidence rate in the population

- `Study_Incidence_Rate`: estimated age specific incidence rate in the study

- `Category_Results`: observed and predicted absolute risks and observed and predicted relative risks in each category defined by the risk score

- `Category_Specific_Observed_Absolute_Risk`: Observed absolute risk in each category defined by the risk score

- `Category_Specific_Predicted_Absolute_Risk`: Predicted absolute risk in each category defined by the risk score

- `Category_Specific_Observed_Relative_Risk`: Observed relative risk in each category defined by the risk score

- `Category_Specific_Predicted_Relative_Risk`: Predicted relative risk in each category defined by the risk score

- `Variance_Matrix_Absolute_Risk`: Variance-covariance matrix of the vector of cateogry specific absolute risks

- `Variance_Matrix_LogRelative_Risk`: Variance-covariance matrix of the vector of cateogry specific relative risks

- `Hosmer_Lemeshow_Results`: results of the Hosmer-Lemeshow type chisquare test comparing the observed and predicted absolute risks

- `HL_pvalue`: pvalue of the Hosmer-Lemeshow type chisquare test

- `RR_test_result`: results of the chisquare test comparing the observed and predicted relative risks

- `RR_test_pvalue`: pvalue of the chisquare test of relative risk

- `AUC`: estimate of the Area Under the Curve (AUC) defined as the probability that for a randomly sampled case-control pair the case has a higher risk score than the control; for the full cohort setting we compute the empirical proportion and for the nested case-control setting we compute the inverse probability weighted estimator

- `Variance_AUC`: estimate of the variance of Area Under the Curve (AUC): for the full cohort setting the regular asymptotic variance is estimated and for the nested case-control setting the influence function based variance estimate of the inverse probability weighted variance estimator is computed

- `CI_AUC`: 95 percent Wald based confidence interval of Area Under the Curve (AUC) using the asymptotic variance

- `Overall_Expected_to_Observed_Ratio`: The overall ratio of the expected risk to the observed risk

- `CI_Overall_Expected_to_Observed_Ratio`: 95 percent Wald based confidence interval of the overall ratio of the expected risk to the observed risk

### See Also

`computeAbsoluteRisk`

### Examples

    data(bc_data, package="iCARE")
    validation.cohort.data$inclusion = 0
    subjects_included = intersect(validation.cohort.data$id,
                                  validation.nested.case.control.data$id)
    validation.cohort.data$inclusion[subjects_included] = 1

    validation.cohort.data$observed.followup = validation.cohort.data$study.exit.age -
      validation.cohort.data$study.entry.age

    selection.model = glm(inclusion ~ observed.outcome
                          * (study.entry.age + observed.followup),
                          data = validation.cohort.data,
                          family = binomial(link = "logit"))

    validation.nested.case.control.data$sampling.weights =
      selection.model$fitted.values[validation.cohort.data$inclusion == 1]

    set.seed(50)

    data = validation.nested.case.control.data

    snpDat     = bc_72_snps
    form       = diagnosis ~ famhist + as.factor(parity)
    info       = list(bc_model_cov_info[[1]], bc_model_cov_info[[3]])
    vars       = all.vars(form)[-1]
    risk.model = list(model.formula = form,
                      model.cov.info = info,
                      model.snp.info = snpDat,
                      model.log.RR = bc_model_log_or[c(1, 8:11)],
                      model.ref.dataset = ref_cov_dat[, vars],
                      model.ref.dataset.weights = NULL,
                      model.disease.incidence.rates = bc_inc,
                      model.competing.incidence.rates = mort_inc,
                      model.bin.fh.name = "famhist",
                      apply.cov.profile = data[,vars],
                      apply.snp.profile = data[,snpDat$snp.name],
                      n.imp = 5, use.c.code = 1, return.lp = TRUE,
                      return.refs.risk = TRUE)

    # Not run since it can take a few minutes
    # output = ModelValidation(study.data = data, total.followup.validation = TRUE,
    #      predicted.risk.interval = NULL, iCARE.model.object = risk.model,
    #      number.of.percentiles = 10)
    output

[Package iCARE version 1.20.0 Index]