Colonoscopy yields fewer polyps as the day progresses despite using social influence theory to reverse the trend

Background We previously reported that fewer polyps are detected by colonoscopy as the day progresses, a phenomenon that could be modified with “social influence theory” by using auditing and feedback. Objective To measure the impact of a social influence informational poster on the relationship between time of day and colonoscopy yield. Design Controlled before-and-after study comparing the polyp yield and time of day relationship in a historical cohort versus a 3-month intervention period. Setting University-based Veterans Affairs medical center. Patients Patients undergoing outpatient screening, surveillance, or diagnostic colonoscopies. Intervention Placement of informational posters in endoscopy rooms within view of operators and nurses. The poster depicted a bar graph of the previously documented hour-by-hour decreases in polyp yield coupled with prominent text: “What Time Is It Now?” Main Outcome Measurement Polyp yield, including secondary end point limited to adenoma detection. We performed regression to measure the effect of start time on polyp yield. Results There were 477 and 301 patients in the control and intervention periods, respectively. There was a negative relationship between start time and polyp yield, including adenoma detection, for both periods ( P = .001). Start time remained negatively predictive of polyp and adenoma yield after adjusting for poster exposure and confounders ( P = .01). Limitations Nonrandomized study design. Conclusion An informational poster did not alter the relationship between colonoscopy start time and polyp yield. This strengthens the previous finding that start time may affect polyp yield and suggests that passive use of social influence theory is inadequate to modify this effect. Shortening endoscopy shifts and active auditing with feedback may be necessary.