[The value of hemoglobin A1c for diagnosis of diabetes mellitus and other changes in carbohydrate metabolism in women with recent gestational diabetes mellitus]

Abstract

Introduction: Women with gestational diabetes mellitus (GDM) have an increased risk for developing diabetes mellitus (DM). Their postpartum metabolic classification using a 75g oral glucose tolerance test (75g OGTT) is recommended. The purpose of this study was to assess the value of hemoglobin A1c for postpartum evaluation in women with recent gestational diabetes mellitus.

Patients and methods: Fifty-six women with recent GDM underwent a 75g OGTT at our center to assess postpartum changes in carbohydrate metabolism and were classified using diagnostic criteria of the American Diabetes Association (ADA). Receiver operating characteristic (ROC) curves analysis was used to assess the diagnostic performance of hemoglobin A1c, and kappa index was used to evaluate diagnostic agreement between hemoglobin A1c and 75g OGTT.

Results: DM was diagnosed in 7 women, and other categories of increased risk for DM in 25 women. Kappa index for diagnosis agreement was 0,22. Hemoglobin A1c ≥ 5.7% had 47% sensitivity and 71% specificity for identifying any change in carbohydrate metabolism. A hemoglobin A1c value ≥ 6.5 had 29% sensitivity and 100% specificity for diagnosis of DM. Area under the ROC curve was 0.57 for identifying any change in carbohydrate metabolism and 0.81 for diagnosis of DM.

Conclusion: Using ADA cutoff values, hemoglobin A1c is not appropriate for postpartum glucose tolerance evaluation in women with recent gestational diabetes mellitus.