Requesting a unique personal identifier or providing a souvenir incentive did not affect overall consent to health record linkage: evidence from an RCT nested within a cohort

Abstract Objective It is unclear if unique personal identifiers should be requested from participants for health record linkage: this permits high-quality data linkage but at the potential cost of lower consent rates due to privacy concerns. Study Design and Setting Drawing from a sampling frame based on the FAMILY Cohort, using a 2 × 2 factorial design, we randomly assigned 1,200 participants to (1) request for Hong Kong Identity Card number (HKID) or no request and (2) receiving a souvenir incentive (valued at USD4) or no incentive. The primary outcome was consent to health record linkage. We also investigated associations between demographics, health status, and postal reminders with consent. Results Overall, we received signed consent forms from 33.3% (95% confidence interval [CI] 30.6–36.0%) of respondents. We did not find an overall effect of requesting HKID (−4.3%, 95% CI −9.8% to 1.2%) or offering souvenir incentives (2.4%, 95% CI −3.1% to 7.9%) on consent to linkage. In subgroup analyses, requesting HKID significantly reduced consent among adults aged 18–44 years (odds ratio [OR] 0.53, 95% CI 0.30–0.94, compared to no request). Souvenir incentives increased consent among women (OR 1.55, 95% CI 1.13–2.11, compared to no souvenirs). Conclusions Requesting a unique personal identifier or providing a souvenir incentive did not affect overall consent to health record linkage.