December 2007

Objectives Evaluation of advance telephone prompting on the response rate to a postal, self-completed questionnaire. To provide an estimate of the cost of such a strategy. Method A sample of 315 GDPs was randomly selected from a randomised database of GDPs practicing in Scotland. 157 GDPs were randomly allocated to receive an advance telephone prompt, via the practice receptionist; 158 were allocated to a control group. Four days after prompting all trial participants were mailed identical questionnaires, cover letter and postage paid return envelope. Results Response rates: 53% - advance telephone prompt group and 40% - control group. The effect size, 13%, was found to be statistically significant, p = 0.026. Total estimated strategy costs: ₤74.00. The incremental cost was estimated to be ₤4.93 for each additional response. Conclusions Advance telephone prompting of GDP’s, via the practice receptionist, statistically significantly improves the response rate to a postal self-completed questionnaire. This is estimated to be a cost effective strategy for improving response rates to postal questionnaires. Key words: Analysis, controlled trial, cost, questionnaire, randomised response rate.