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.