Increasing the response rate of text messaging data collection: a delayed randomized controlled trial

OBJECTIVE To test the effectiveness of multiple interventions on increasing the response rate of text messaging for longitudinal data collection. METHODS Our cohort included 283 caregivers of children aged 6-12 months who were participating in an anemia program in rural China. Using text messages to collect data on anemia medication adherence, we conducted a delayed randomized controlled trial to test multiple interventions (an additional four reminders; a ¥5.0 (US$0.79) credit reward for replying; and a feedback text message). After a 6-week pilot study with week 7 as the baseline measurement, we randomly allocated all participants into two groups: group 1 (n = 142) and group 2 (n = 141). During weeks 8-11, we introduced the interventions to group 1, and in weeks 12-15 the intervention was introduced to both groups. We compared the response rates between groups and explored factors affecting the response rate. RESULTS During weeks 8-11, the response rates in group 1 increased and were significantly higher than in group 2 (p<0.05). During weeks 12-15, the response rate increased significantly in group 2 (p>0.05) and slightly decreased in group 1. Younger participants or participants who had children with lower hemoglobin concentration were more likely to reply (p = 0.02). Sending four reminders on the second day contributed to only 286 (11.7%) extra text messages. DISCUSSION Our study showed that multiple interventions were effective in increasing response rate of text messaging data collection in rural China. CONCLUSIONS Larger multi-site studies are needed to find the most effective way of using these interventions to allow usage of text messaging data collection for health research.