Evaluation of three methods of symptom reporting in a clinical trial of felodipine.

251 patients from 23 primary health care centres were recruited to a clinical trial in which either felodipine or placebo was added to baseline metoprolol treatment. Three methods of symptom reporting were used in 191 patients, namely two previously documented self-administered questionnaires and an adverse event monitoring system (spontaneous reports to treating physician). Higher frequencies of symptoms were seen with the questionnaires compared to spontaneous reporting. However, the overlap between the methods was moderate and they were found to complement one another. The questionnaires were completed twice during the study and the adverse event monitoring system was applied on five occasions. The rate of application had consequences for the ability of each method to detect transient, dose-related symptoms, e.g. headache and dizziness. Regardless of method, the possibility of detecting dose-related symptoms was enhanced when symptoms were measured not only during active treatment but also during a run-in or other baseline period, and both phases were considered in the analyses.