Prior notification of trial participants by newsletter increased response rates: a randomized controlled trial

Objective: To assess the effectiveness of prenotification using a newsletter to increase questionnaire response rates within a randomized controlled trial (RCT).

Study design and setting: An RCT set within the context of the Medical Research Council's SCOOP trial of screening older women for fracture risk.

Results: A subsample of SCOOP participants were randomized in equal numbers to receive a newsletter approximately 6 weeks before the follow-up questionnaire or no newsletter. Of the 1,342 participants in the newsletter group, 1,291 (96.2%) returned their 24-month follow-up questionnaire compared with 1,271 of the 1,344 participants who were not allocated to receive the newsletter (94.6%). The difference of 1.6% was statistically significant (P=0.05), with an odds ratio (OR) of 1.45 (95% confidence interval [CI]: 1.01, 2.10). The newsletter and no newsletter groups required a similar number of reminders (OR 0.88, 95% CI: 0.73, 1.06), had a similar number with a complete primary outcome (OR 0.95, 95% CI: 0.57, 1.58), and took a similar time to respond (log rank 1.30, P=0.25).

Conclusions: This study supports previous research that suggests that prenotification increases survey response rate: albeit a small absolute increase. No previous study has shown this to be so within the context of patients enrolled within an RCT. Trials that use newsletters to keep their participants informed of the study's progress should use the newsletter as a prenotification device as this will increase overall response rates.