model_validation: Model Validation

In wheelerb/iCARE: A Tool for Individualized Coherent Absolute Risk Estimation (iCARE)

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$inclusion = 0
tmp = match(as.character(validation.cohort.data$id), validation.nested.case.control.data$id)
tmp = tmp[!is.na(tmp)]
validation.cohort.data$inclusion[tmp] = 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)

bc_model_formula = observed.outcome ~ famhist + as.factor(parity)
data = validation.nested.case.control.data

risk.model = list(model.formula = bc_model_formula,
                  model.cov.info = bc_model_cov_info,
                  model.snp.info = bc_15_snps,
                  model.log.RR = bc_model_log_or,
                  model.ref.dataset = ref_cov_dat,
                  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[,all.vars(bc_model_formula)[-1]],
                  apply.snp.profile = data[,bc_15_snps$snp.name],
                  n.imp = 5, use.c.code = 1, return.lp = TRUE,
                  return.refs.risk = TRUE)

output = ModelValidation(study.data = data,
                          total.followup.validation = TRUE,
                           predicted.risk.interval = NULL,
                           iCARE.model.object = risk.model,
                           number.of.percentiles = 10)

wheelerb/iCARE documentation built on May 17, 2019, 2:02 p.m.