Abstract

Studies for assessing non-inferiority of a new diagnostic test relative to a standard test typically use a complete matched-pairs design in which results for both tests are obtained for all subjects. We present alternative non-inferiority tests for the situation where results for the standard test are obtained for all subjects but results for the new test are obtained for a subset of those subjects only. This situation is common when results for the standard test are available from a monitoring or screening programme or from a large biobank. A stratified sampling procedure is presented for drawing the subsample of subjects that receive the new diagnostic test with strata defined by the two outcome categories of the standard test. Appropriate statistical tests for non-inferiority of the new diagnostic test are derived. We show that if diagnostic test positivity is low, the number of subjects to be tested with the new test is minimized when stratification is non-proportional.