A randomized trial of the impact of telephone and recorded delivery reminders on the response rate to research questionnaires.

Background: A range of factors have been shown to affect the response rate to mailed questionnaires, but particular strategies to improve patients' response in trials conducted in general practice require further study.

Methods: Non-responders in a larger trial were randomized to receive a telephone or recorded delivery reminder on the third contact. The cost of administration of each method was estimated.

Results: Significantly more patients returned completed questionnaires when sent questionnaires by recorded delivery, although the cost per patient contacted was nearly three times more than for contact by telephone.

Conclusion: Our study indicates that sending reminders by recorded delivery, although more expensive, is more effective than telephone reminders for recruiting patients to a study in general practice using research questionnaires.