Poor accuracy of HbA1c for the diagnosis of prediabetes in overweight and obese Bangladeshi adults

Background/Purpose

The aim of the study was to assess the effect of obesity on the diagnostic accuracy of HbA1c.

Methods

This retrospective cross sectional study was conducted in 108 overweight/obese and 40 normal weight Bangladeshi adults. Those satisfying the exclusion and inclusion criteria were included. Diabetes and pre-diabetes were diagnosed by oral glucose tolerance test (OGTT) and HbA1c using the 2006 World Health Organization (WHO) diagnostic criteria. HbA1c was estimated by capillary electrophoresis method.

Results

108 overweight and obese (mean body mass index (BMI) 36.33 ± 8.86 kg/m², mean age 29.12 ± 9.28 years) and 40 normal weight (mean BMI 20.35 ± 1.68 kg/m², mean age 28.13 ± 6.22 years) adults were included in the study. Significantly greater number of patients were diagnosed with prediabetes using HbA1c criteria than OGTT criteria (39.68% vs 19.05%, p = 0.005) in overweight and obese group. The concordance between OGTT and HbA1c for the diagnosis of prediabetes was low in overweight and obese adults [Ƙ with 95%CI = 0.031(-0.194 to 0.256), n = 52]. The specificity and discrimination of HbA1c for the diagnosis of prediabetes were low in overweight and obese compared to normal weight group (52.3% vs 93.9%; 0.64 vs 0.89, p = 0.056, 95% CI = -0.01 to 0.51, respectively). The specificity of HbA1c for the diagnosis of prediabetes in adults with BMI ≥ 23 kg/m² increased to 90% at a cut-off of 6.15%.

Conclusion

HbA1c was not accurate in the diagnosis of prediabetes in adults with BMI ≥ 23 kg/m². A higher cut-off value for HbA1c should be used for the diagnosis of prediabetes, but not diabetes.