What proportion of patients refuse consent to data collection from their records for research purposes?

Abstract

In a randomised trial of the implementation of guidelines for asthma and angina, we sent questionnaires that included a request for consent to collect data from the patient's clinical records to 5069 patients in 81 general practices. Of these 3429 (67.6%) responded, of whom 335 (9.8% [95%, CI = 8.8%-10.8%]) refused consent. We conclude that consent should always be sought unless a research ethics committee has waived this requirement for pressing reasons.