Early postpartum HbA1c after hyperglycemia first detected in pregnancy - imperfect but not without value

Abstract

AbstractBackgroundSouth Africanwomen of childbearing age are disproportionally affected by obesity and at significant risk of Type 2 Diabetes Mellitus (T2DM). Unless pregnant, they do not readily undergo screening for T2DM. With a local focus on improved antenatal care, hyperglycemia is often first detected in pregnancy (HFDP). This may erroneously be attributed to Gestational Diabetes Mellitus (GDM) in all without considering T2DM. Glucose evaluation following pregnancy is essential for early detection and management of women with T2DM in whom persistent hyperglycemia is to be expected. Conventional testing with an oral glucose tolerance test (OGTT) is cumbersome, prompting investigation for alternate solutions.AimTo compare the diagnostic performance of HbA1c to the current gold standard OGTT in women with HFDP 4-12 weeks post-delivery.MethodsGlucose homeostasis was assessed with OGTT and HbA1c in 167 women with HFDP, 4-12 weeks after delivery. Glucose status was based on American Diabetes Association criteria.ResultsGlucose homeostasis was assessed at 10 weeks (IQR 7-12) after delivery. A total of 52/167 (31%) participants had hyperglycemia, 34 (20%) had prediabetes, and 18 (11%) had T2DM. For patients with prediabetes, fasting plasma glucose (FPG) and 2 hour plasma glucose (2hPG) were diagnostic in 12 patients, whereas in two-thirds (22/34) only one time point was diagnostic. FPG and 2hPG values were both in the prediabetes diagnostic range in six women with T2DM. Based on FPG, 15 women with persistent hyperglycemia (11 with prediabetes and four with T2DM) would have been missed (15/52; 29%). The HbA1c accurately classified 85% of the 52 participants with gold standard OGTT defined hyperglycemia and 15 of 18 women with postpartum persistent T2DM. When compared to an OGTT, a single HbA1c of 6.5% (48mmol/mol) postpartum demonstrated a sensitivity of 83% and specificity of 97% for the identification of T2DM.ConclusionHbA1c may improve access to postpartum testing in overburdened clinical settings where the required standards of OGTT cannot be guaranteed. HbA1c is a valuable test to detect women who will benefit most from early intervention but cannot unequivocally replace OGTT.