Association of variants with hemoglobin A1c and impact on diabetes diagnosis in East Asian individuals.

OBJECTIVE

Hemoglobin A1c (HbA1c) accuracy is important for diabetes diagnosis and estimation of overall glycemia. The Asahi variant which causes glucose-6-phosphate dehydrogenase (G6PD) deficiency has been shown to lower HbA1c independently of glycemia in African ancestry populations. As different variants occur in Asian ancestry, we sought to identify Asian-specific variants associated with HbA1c.

RESEARCH DESIGN AND METHODS

In eight Asian population-based cohorts, we performed imputation on the X chromosome using the 1000 Genomes reference panel and tested for association with HbA1c (10 005 East Asians and 2051 South Asians). Results were meta-analyzed across studies. We compared the proportion of individuals classified as having diabetes/pre-diabetes by fasting glucose ≥100 mg/dL or HbA1c ≥5.7% units among carriers and non-carriers of HbA1c-associated variants.

RESULTS

The strongest association was a missense variant (-Canton, rs72554665, minor allele frequency=2.2%, effect in men=-0.76% unit, 95% CI -0.88 to -0.64, p=1.25×10, n=2844). Conditional analyses identified a secondary distinct signal, missense variant (-Kaiping, rs72554664, minor allele frequency=1.6%, effect in men=-1.12 % unit, 95% CI -1.32 to -0.92, p=3.12×10, p=7.57×10). Adjusting for glucose did not attenuate their effects. The proportion of individuals with fasting glucose ≥100 mg/dL did not differ by carrier status of -Canton (p=0.21). Whereas the proportion of individuals with HbA1c ≥5.7% units was lower in carriers (5%) compared with non-carriers of -Canton (30%, p=0.03).

CONCLUSIONS

We identified two variants in East Asian men associated with non-glycemic lowering of HbA1c. Carriers of these variants are more likely to be underdiagnosed for diabetes or pre-diabetes than non-carriers if screened by HbA1c without confirmation by direct glucose measurements.