Glycated hemoglobin (HbA1c) in diagnosis of gestational diabetes mellitus

Objective: To evaluate the diagnostic accuracy of glycated hemoglobin for diagnosing gestational diabetes mellitus. Material and Methodology: This cross-sectional comparative study was conducted at the Department of Chemical Pathology and Endocrinology, Reference Laboratory, Rawalpindi from June 2023 to October 2023. The study included women having gestational amenorrhea between 24th to 28th weeks, who gave informed written consent for a 75-gram oral glucose tolerance test (OGTT) at Reference Laboratory Rawalpindi. Women with diabetes, hypertension, hemoglobin< 10g/dl, on steroid treatment, with gastrointestinal or thyroid diseases were excluded. The medical history and anthropometric measurement (height, weight, body mass index (BMI) and blood pressure were recorded on a predesigned proforma. Blood sample for glucose was taken in sodium fluoride tubes and HbA1c in potassium EDTA tubes. American Diabetes Association criteria 2023 was used to diagnose gestational diabetes mellitus (GDM). Study participants were divided into two groups on basis of 75g- OGTT results; Group 1 included GDM and Group 2 Normal Glucose Tolerance (NGT). Results: A total of 100 pregnant ladies were enrolled whose ages ranged from 15-45 (mean & SD 29±5 & 31±6 years in groups 1& 2 respectively). Mean fasting plasma glucose (FPG) was 5.11±0.6 mmol/l & 4.57±0.4mmol/l, and HbA1c was 6.12%±1 & 5.26% ±0.48 in groups 1& 2 respectively. GDM was found in 19 (group 1) of 100 patients, while 81 responded normally. HbA1c at 5.6% has 84.2% sensitivity, 87.6% specificity, 61.5% PPV, 95.9% NPV and 87% diagnostic accuracy. FPG, 1hr glucose and HbA1c exhibited an Area Under Curve (AUC) by Receiver Operating Characteristic (ROC) Curve of 0.762, 0.801 & 0.894 respectively. Conclusion: HbA1c has shown higher diagnostic yield for gestational diabetes mellitus and can be used as a screening test. Keywords: Glycated hemoglobin, Oral glucose tolerance test, Gestational diabetes mellitus