We defined the consent rates for a given study as the number of individuals in each reported racial or ethnic group who agreed to participate in the study divided by the number of individuals in that group who were invited to participate. The identified studies classified minority groups in four different ways: (1) African-Americans and Hispanics classified separately; (2) only African-Americans classified; 3) African-Americans classified separately and all other minorities grouped together; 4) all minorities grouped together. Because the original studies used different race/ethnic classifications, the minority group(s) to which non-Hispanic whites are compared in the present analysis varies across the studies.
