Moving to an HbA1c based diagnosis of diabetes has a different impact on prevalence in different ethnic groups

Abstract

Objective: To compare screen detected diabetes prevalence and the degree of diagnostic agreement by ethnicity with the current OGTT-based and newly proposed HbA_1c-based diagnostic criteria. Research design and methods: Six studies (1999-2009) from Denmark, United Kingdom, Australia, Greenland, Kenya, and India were tested for the probability of an HbA_1c ≥ 6.5% among diabetes cases based on an OGTT. The difference in probability between centers was analyzed by logistic regression adjusting for relevant confounders. Results: Diabetes prevalence was lower with the HbA_1c-based diagnostic criteria in four out of six studies. The probability of an HbA_1c ≥ 6.5% among OGTT-diagnosed cases ranged widely (17.0 to 78.0%) by study center. Differences in diagnostic agreement between ethnic sub-groups in the United Kingdom study were of the same magnitude as between-country comparisons. Conclusions: A shift to an HbA_1c-based diagnosis for diabetes will have substantially different consequences for diabetes prevalence across ethnic groups and populations.