How Many Patients Do We Need? Predictors of Consent to Participate in Clinical Research Studies in Orthopaedic Trauma.

Objectives: To characterize the recruitment rates at a Level I trauma center enroling for multiple prospective orthopaedic trauma research studies and identify patient-related and study-related predictors of consent.

Design: We conducted a case-control study to identify predictors of study consent. The authors categorized studies based on intensity of the study intervention (low, intermediate, or high). A 2-level generalized linear model with random intercept for study was used to predict study consent.

Setting: This analysis includes data from 10 federally funded studies conducted as part of a large, national consortium that were enroling patients in 2013-2014.

Patients/participants: Three hundred thirty-four patients were approached for at least 1 study and included in the analysis.

Intervention: N/A.

Main Outcome Measures: Consent to participate in the research study.

Results: A total of 315 patients consented to be in a study (71% of approached patients). Consent rate varied by study (45%-95%). No patient characteristics (race, age, or sex) were associated with consent. Patients approached for studies of intermediate intensity were 83% less likely to consent (odds ratio = 0.17; 95% confidence interval: 0.04-0.67), and those approached for studies of high intensity were 91% less likely to consent (odds ratio = 0.09; 95% confidence interval: 0.03-0.32).

Conclusion: Patient factors were not associated with consent. Study intensity is a major driver of consent rates. Studies of higher intensity will require the study team to approach up to twice as many patients as the target enrolment. This study provides a framework that can be used in study planning and determination of feasibility.