The Gini coefficient as a measure for understanding accrual inequalities in multicenter clinical studies.

摘要

OBJECTIVE: Clinical sites participating in multicenter trials may have unequal performance in recruiting subjects. We propose using the Gini coefficient as a quantitative measure of site accrual inequalities. STUDY DESIGN AND SETTING: We evaluated the relationship of this metric to other study characteristics across 166 clinical studies (27,865 subjects) conducted by the AIDS Clinical Trials Group between 1986 and 1999. RESULTS: Overall there was a modest recruitment inequality among clinical centers (mean Gini=0.33). In multivariate modeling, site accrual inequalities were higher when there was more protracted enrollment, and a larger number of sites and were lower in antiretroviral studies than other studies. In long-term studies, the site accrual inequality increased significantly over time (P=0.004). In efficacy trials, a higher Gini coefficient was associated with higher likelihood of the study results being statistically significant (P=0.010). CONCLUSION: The Gini coefficient may be easily and routinely incorporated in the description of the characteristics of a clinical study and may provide insights about its enrollment pattern.