Differences in A1C by race and ethnicity among patients with impaired glucose tolerance in the Diabetes Prevention Program.

OBJECTIVE: We sought to examine racial and ethnic differences in A1C in individuals with impaired glucose tolerance (IGT). RESEARCH DESIGN AND METHODS: We studied 3,819 individuals aged > or = 25 years with IGT who were found to be eligible to participant in the Diabetes Prevention Program. A1C was compared among five racial and ethnic groups before and after adjustment for factors that differed among groups or might affect glycemia including age, sex, education, marital status, blood pressure, adiposity (BMI and waist circumference), hematocrit, fasting and post-glucose load glucose levels, glucose area under the curve (AUC), beta-cell function, and insulin resistance. RESULTS: Mean +/- SD A1C was 5.91 +/- 0.50%. Among whites, A1C was 5.80 +/- 0.44%, among Hispanics 5.89 +/- 0.46%, among Asian 5.96 +/- 0.45%, among American Indians 5.96 +/- 0.46%, and among blacks 6.19 +/- 0.59%. Age, sex, systolic blood pressure, diastolic blood pressure, BMI, fasting glucose, glucose AUC, corrected insulin response, and insulin resistance were each independent predictors of A1C. Adjusting for these and other factors, mean A1C levels were 5.78% for whites, 5.93% for Hispanics, 6.00% for Asians, 6.12% for American Indians, and 6.18% for blacks (P < 0.001). CONCLUSIONS: A1C levels are higher among U.S. racial and ethnic minority groups with IGT after adjustment for factors likely to affect glycemia. Among patients with IGT, A1C may not be valid for assessing and comparing glycemic control across racial and ethnic groups or as an indicator of health care disparities.

The Diabetes Prevention Program: recruitment methods and results.

The Diabetes Prevention Program (DPP) is a multicenter randomized controlled trial designed to test whether diet and exercise or medication can prevent or delay the onset of type 2 diabetes in persons with impaired glucose tolerance, who are at increased risk of the disease. This paper describes DPP recruitment methods, strategies, performance, and costs. The DPP developed an organizational structure for comprehensive management and continuous monitoring of recruitment efforts. The DPP utilized a variety of recruitment strategies, alone or in combination, and a stepped informed consent procedure leading to randomization. Studywide and clinic-specific recruitment data were monitored, analyzed, and used to modify recruitment approaches. DPP recruitment was completed slightly ahead of schedule, meeting goals for the proportion of women enrolled and nearly meeting goals for the proportion of racial/ethnic minorities. Clinics varied widely in the recruitment strategies they used, and these strategies also varied by participant age, gender, and race/ethnicity. Staff time devoted to recruitment averaged 86.8 hours per week per clinic, with the majority of effort by staff specifically assigned to recruitment. The number of staff hours required to recruit a participant varied by recruitment strategy. Recruitment cost (excluding staff cost) was about 1075 US dollars per randomized participant. The DPP experience offers lessons for those planning similar efforts: (1) a method for ongoing assessment and revision of recruitment strategies is valuable; (2) a range of recruitment strategies may be useful; (3) the most effective methods for recruiting potential subjects may vary according to the gender, age, and race/ethnicity of those individuals; (4) recruitment strategies vary in the amount of staff time required to randomize a participant; and (5) a stepped screening may make it easier to identify and recruit volunteers who understand the requirements of the study.