Randomized trial within a trial of yellow 'post-it notes' did not improve questionnaire response rates among participants in a trial of treatments for neck pain

Rationale: Attrition is a threat to the validity of randomized trials. Few randomized studies have been conducted within randomized trials to test methods of reducing attrition.

Aim: To test whether using yellow post-it notes on follow-up questionnaires in the ATLAS treatment trial for neck pain reduces attrition.

Method: Nested trial within a trial. ATLAS participants were randomized to have their 6-month follow-up questionnaire have a 3' yellow post-it note with a handwritten message encouraging return of questionnaire.

Results: 499 participants were independently randomized using simple allocation to receive the post-it notes or not. Two hundred fifteen of the 256 (84.0%) participants in the intervention group returned their questionnaire compared with 205 of the 243 (84.4%) in the control group. There was no difference in time to response.

Conclusion: Yellow post-it notes do not enhance questionnaire return rates for participants in a randomized trial of neck pain.