Estimation of risk ratios in case-base studies with competing risks.

The case-base study is a recently developed modification of the case-control design that leads to risk ratio estimates. Currently available methods for the analysis of case-base studies lead to estimates of the unconditional risk ratio which may be misleading of censoring occurs. In this manuscript, we describe an approach for the analysis of case-base studies that yields conditional risk ratio estimates which remain valid in the presence of censoring. The approach we propose for estimating risk ratios and their standard errors involves a non-iterative procedure.