Evaluation of the Combination of HbA1C with Hematocrit for Early Screening of Gestational Diabetes Mellitus

Background & Objective: Gestational diabetes mellitus (GDM) is the most prevalent disorder during pregnancy, which is the result of insulin resistance and hyperinsulinemia due to the secretion of placental diabetogenic hormones. This study aimed to investigate the utility of glycated hemoglobin A1c (HbA1c) alone and in combination with hematocrit for early detection of gestational diabetes mellitus. Materials & Methods: In this prospective cohort research, 373 pregnant women who referred to prenatal clinics were included. Hematocrit and HbA1c were determined at gestational age of 12 to 16 weeks and compared with the oral glucose tolerance test (OGTT) results at gestational age of 24-28 weeks. Results: The best cut-off point hematocrit for determining pregnancy diabetes mellitus was 37.3. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 70.15%, 64.12%, 32.71 %, and 89.51% respectively. In terms of HbA1c, the best cut-off value to determine GDM in pregnant women was 5, with a sensitivity of 98.51%, specificity rate of 99.02%, PPV of 95.07%, and NPV of 99.49%. In terms of diagnosing GDM, the area under the ROC curve (AUC) for HbA1c was equal to 0.985 which was higher than the AUC for the combination of HbA1c with HCT. Conclusion: Measuring HbA1c can be useful as a screening test for GDM, which is an inexpensive and available test. The combined evaluation of HbA1c and hematocrit did not improve the diagnostic value of HbA1c in GDM screening compared to exclusive evaluation of HbA1c.