Hemoglobin A1c in early postpartum screening of women with gestational diabetes

AIM:To assess the utility of hemoglobin A1c(HbA1c) in the early postpartum screening of women with gestational diabetes mellitus(GDM).METHODS:Over a 3 years period,HbA1c estimations were undertaken in addition to and simultaneously with the traditional oral glucose tolerance test(OGTT),in 203 women with GDM as a part of early postpartum screening for dysglycaemia,at 6 wk post-partum.World Health Organization criteria was used for diagnosing diabetes:fasting blood glucose(FBG) ≥ 7.0 mmol/Land/or 2-h postprandial blood glucose(PPBG) ≥ 11.1 mmol/L and/or HbA1c ≥ 48 mmol/mol;and impaired glycaemiastate:impaired fasting glucose 6.1-6.9 mmol/L and/or impaired glucose tolerance 7.8-11.0 mmol/L and/or HbA1c:42-47 mmol/mol.RESULTS:Mean FBG,2-h PPBG and HbA1c were 4.9 ± 0.7 mmol/L,5.6 ± 2.0 mmol/L and 38 ± 5 mmol/mol respectively.FBG,2-h PPBG and HbA1c detected 6(3%),7(3.5%) and 11(5.4%) cases of diabetes respectively,and 11(5.4%),25(12.3%) and 23(11.3%) cases of pre-diabetes state respectively.HbA1c values ≥ 48 mmol/mol(≥ 6.5%) showed a diagnostic sensitivity of 71.4% and specificity of 98.5% for diabetes in comparison to OGTT in receiver operating characteristics curve analysis.At HbA1c cut-off 44 mmol/mol,sensitivity and specificity were 100% and 92.3% respectively [area under the curve:0.98(95%CI:0.96-1.00)].Sensitivity and specificity for detecting high risk "impaired glycaemia" state [HbA1c 42 mmol/mol(6.0%)] were 28% and 80%,respectively.CONCLUSION:HbA1c level ≥ 48 mmol/mol(≥ 6.5%) has reasonable sensitivity and high specificity in comparison to OGTT for early postpartum screening of diabetes in GDM.At 6 th week postpartum screening,if FBG is normal and HbA1c < 44 mmol/mol OGTT is not recommended.