Frequency of HLA-DQB*06 in Caucasian,African American, and Mexican American patients with a positive direct antiglobulin test.

A reduced frequency of HLA-DQ6 in patients with a positive direct antiglobulin test (DAT) was previously reported but race was undisclosed. Therefore, we investigated a total of 275 patients (80 Caucasian, 113 African American, and 82 Mexican American) and 518 normal controls (205 Caucasian, 208 African American, and 105 Mexican American). These were typed for class II HLA antigens using molecular techniques. A DAT was performed on each patient's red cells drawn into EDTA using both mouse and rabbit polyspecific reagents. Of 275 patients tested, 73 (27%) had a positive DAT (12 Caucasians, 35 African Americans, and 26 Mexican Americans). We found that 5 (42%) Caucasian patients and 103 (50%) Caucasian controls possessed the DQB*06 allele (p =.56). In the African American group, 15 (43%) patients and 91 controls (44%) were DQB*06 positive (p =.92). Six Mexican American patients (23%) and 21 controls (20%) had the DQB*06 allele (p =.72). This article underscores the need to use race-matched controls when genetic disease associations are sought.