Text message reminders to improve questionnaire response rates.
OBJECTIVES To assess whether short message service (SMS) text messages sent as prenotification or postnotification reminders improve questionnaire response rates in randomized controlled trial (RCT) follow up. STUDY DESIGN AND SETTING Three "trials within a trial" assessed text message notifications sent before or after receipt of a follow up questionnaire within an RCT for patients with depression. Consenting patients (n 523) were randomized to receive a prenotification or no notification at 3 months, prenotification or postnotification at 6 months, and a postnotification or no notification at 12 month follow up. Unadjusted and adjusted questionnaire return rates and time to return were compared. RESULTS The two trials comparing prenotification or postnotification with no notification at 3 and 9 month follow up found no evidence of an effect on questionnaire response rates (3 month response rate: 82.9% vs. 84.7% (difference 1.79% 95% confidence interval [CI] 4.53% to 8.11% P 0.58) 9 month response rate: 77.1% vs. 78.5% (difference 1.44% 95% CI 8.56% to 5.67% P 0.69) For the trial at 6 month follow up, there was a statistically significant difference in response rates for postnotification (83.2% compared with prenotification (75.2% (difference 7.95% 95% CI 1.00% to 14.91% P 0.02) CONCLUSION SMS as a prenotification device seems ineffective. For postnotification, the evidence is unclear.
Journal of clinical epidemiology