RESULTS	The TT genotype frequency varied from 1.2 % ( 95 % CI : 0.7 , 2.0 ) in non-Hispanic blacks and 11.6 % ( 95 % CI : 9.6 , 14.0 ) in non-Hispanic whites to 19.4 % ( 95 % CI : 16.7 , 22.3 ) in Mexican Americans .\