We found that risk functions based on routinely measured clinical variables better discriminated incident type 2 diabetes cases than did a panel of 20 diabetes associated single nucleotide polymorphisms. The inclusion of genetic information in the risk models did not improve the discrimination of cases of type 2 diabetes, and nor did it provide clinically important improvement in the accuracy of these models when assessed by calibration. The addition of genetic data to phenotype based risk models also provided minimal net reclassification improvement. The addition of genetic information resulted in the reassortment of people into different risk categories, but not all the shifts were helpful. Although some eventual cases were upgraded to higher risk categories, almost as many had their risk downgraded, and the opposite was true for many of those who remained healthy.
