Published online Jun 15, 2013. doi: 10.4239/wjd.v4.i3.76
Revised: March 26, 2013
Accepted: May 16, 2013
Published online: June 15, 2013
Processing time: 118 Days and 11.1 Hours
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/L and/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 6th week postpartum screening, if FBG is normal and HbA1c < 44 mmol/mol OGTT is not recommended.
Core tip: Hemoglobin A1c (HbA1c) though accepted as a screening tool for diagnosis of diabetes by professional bodies, its role in early postnatal screening of women with gestational diabetes mellitus is not known, which is explored in this study. Analysing the results of simultaneous oral glucose tolerance test (OGTT) and HbA1c estimations undertaken as a part of postpartum screening at 6 wk, we note that HbA1c has a high negative predictive value and can help in excluding diabetes (but not impaired glycaemia). We thus propose that HbA1c could potentially be used with fasting blood glucose estimation to avoid OGTT in those women with an HbA1c < 44 mmol/mol.