Questioning Patients About Adverse Medical Events: A Randomized Controlled Trial

214 patients involved in a larger randomized controlled trial of the herb, saw palmetto, for benign prostatic hyperplasia were randomly assigned to 3 different methods of adverse event ascertainment after a 1-month placebo run-in visit. Two methods of ascertainment were open ended questions, and 1 was a checklist. Patients were blinded to group assignment, but investigators were aware (single blind). All patients had taken placebo for one month, but had been told it was a study drug (single blind).