Please cite this paper as: Fox C, Khan K, Coomarasamy A. How to interpret randomised trials of test–treatment combinations: a critical evaluation of research on uterine Doppler test to predict, and aspirin to prevent, pre-eclampsia. BJOG 2010;117:801–808.
The methodology to evaluate either a test or treatment is well developed and understood. However, the design, conduct and interpretation of a combination of a test and a treatment in a single study are fraught with complexities. There are two distinct study designs to evaluate test–treatment combinations, with randomisation occurring either before or after the test. We present critical issues that need to be considered when evaluating and appraising test–treatment combinations, using the example of research on the uterine artery Doppler test to predict, and aspirin to prevent, pre-eclampsia.