Does advance contact with research participants increase response to questionnaires: A Systematic Review and meta-Analysis

Background: Questionnaires remain one of the most common forms of data collection in epidemiology, psychology and other human-sciences. However, results can be badly affected by non-response. One way to potentially reduce non-response is by sending potential study participants advance communication. The last systematic review to examine the effect of questionnaire pre-notification on response is ten years old, and lacked a risk of bias assessment. Objectives: Update Edwards et al. (2009) to include 1) recently published studies, 2) an assessment of risk of bias. Methods: Data sources: Edwards et al. (2009); 13 data-bases; the references in, and citations of included studies. Eligibility criteria: Randomised control trials examining the impact of pre-notification on response. Data extraction: data extraction was done twice by a single unblinded reviewer. Risk of bias was assessed using the Cochrane Risk of Bias tool and funnel plots. Results: 103 trials were included. Over-all pre-notification increased response, OR = 1.38 (95%CI: 1.25-1.53). However, when studies at high or unclear risk of bias were excluded the effect was greatly reduced (OR = 1.11, 95% CI: 1.01-1.21). Conclusions: The evidence implies that while pre-notification does increase response rates, this may not be of clinical utility.