The effect of informed consent on results of a standard upper extremity intake questionnaire

The trend toward requiring explicit consent from patients participating in observational research introduces the potential for consent bias, either through selection bias or through the Hawthorne effect. In the Hawthorne effect, patients may alter responses based on awareness of participation in a study, thus potentially limiting its applicability to a generalized orthopedic practice. We hypothesized that study subjects' awareness of participation in an observational study by informed consent would alter responses to a standard upper extremity questionnaire in a statistically and clinically meaningful way compared with patients who filled out the questionnaire as a quality control measure.

We retrospectively reviewed data on 39 patients who underwent isolated carpal tunnel release, who had completed preoperative and postoperative Quick Disabilities of the Arm, Shoulder, and Hand (Quick DASH) forms without providing consent for study participation. Next, we approached 35 patients scheduled to undergo isolated carpal tunnel release who completed the intake questionnaire on the day of surgery, for consent to participate in the study. After obtaining consent but before surgery, these patients completed a second questionnaire and then completed a postoperative questionnaire at a mean of 8 weeks postoperatively.

There were no significant differences in age, sex, insurance status, symptom duration, nerve conduction study and electromyography results, or disease severity between groups. We identified no statistically significant difference in preoperative or postoperative Quick DASH score between the retrospective and prospective cohorts (40 ± 23 vs 40 ± 19 preoperatively; 27 ± 25 vs 19 ± 13 postoperatively) or within the prospective cohort before and after obtaining informed consent.

Informed consent did not significantly alter patients' responses to the Quick DASH questionnaire. These results suggest that both opt-in and opt-out approaches to observational research in hand surgery provide results that may be applicable to a generalized orthopedic practice.

This study provides evidence that will inform the interpretation of observational research findings in hand surgery.