Diagnostic value of haemoglobin A1c in post-partum screening of women with gestational diabetes mellitus

Abstract

Aims: The aim of this study was to evaluate whether women with gestational diabetes mellitus could be screened using HbA_1c for glucose metabolism status at 6-12 weeks post-partum.

Methods: We enrolled 699 pregnant women diagnosed with gestational diabetes mellitus from October 2005 to December 2013. A 75-g oral glucose tolerance test (OGTT) and HbA_1c measurement were performed at 6-12 weeks after delivery.

Results: The prevalence of overt diabetes and pre-diabetes were 5.2% (n = 36) and 49.1% (n = 343), respectively, when using the 75-g OGTT as the gold standard. HbA_1c alone identified 2.9% (n = 20) as having overt diabetes and 32.2% (n = 225) as having pre-diabetes. When American Diabetes Association cut-offs were applied, the sensitivity and specificity for HbA_1c to diagnose overt diabetes were 19.4% and 98.0%, respectively. Pre-diabetes, according to the HbA_1c criterion, had 41.2% sensitivity and 72.2% specificity. The misclassifications identified 97 positive differences, 233 negative differences and 369 ties (P < 0.05). The area under the receiver operating characteristic curves for detecting diabetes and pre-diabetes were 0.615 [95% confidence interval (95% CI), 0.515 to 0.716] and 0.588 (95% CI, 0.545 to 0.630), respectively.

Conclusions: HbA_1c may not be sensitive enough for an accurate diagnosis, but it is highly specific for diagnosing overt diabetes at 6-12 weeks post-partum in women with previous gestational diabetes mellitus.