Sample sizes for individually matched case-control studies: a group sequential approach.

This paper proposes the use of group sequential methods to calculate sample sizes for individually matched case-control study designs. A table is presented in which the average sample size required for a group sequential (i.e., multistage) matched pair design is compared to that of the conventional matched pair fixed sample size plan for the usual constant relative risk situation. The table shows that group sequential designs are in general more efficient than fixed sample size plans. Computer simulations showed that group sequential methods yield the appropriate type I and type II error rates not only for matching on a one-to-one basis, but also more generally with multiple matched controls per case. Further simulation studies indicated that there may be only a small loss of power when the matching variable(s) is associated with the probability of exposure but not with the disease. This is shown for both the multistage and fixed sample tests.