HbA1c (glycosylated Hemoglobin) – A Screening Method on First Antenatal Visit in Pregnant Women for Gestational Diabetes Mellitus

Abstract

Background: Gestational diabetes mellitus (GDM) is a common medical disorder associated with adverse effect on both mother and neonate. The prevalence of GDM varies from 3.8 to21% across different parts of the country depending upon tests used and population. Early diagnosis and treatment of GDM is of utmost importance to reduce maternal and foetal complications.

Objectives: To ï¬nd the usefulness of Glycosylated hemoglobin (HbA1c) as a screening method for GDM in ï¬rst trimester of pregnancy and to correlate it with 75gm oral glucose tolerance test (OGTT) at 24-28 weeks.

Materials and methods: This was a prospective study carried out in NDMC Medical College and Hindu Rao Hospital. A total of 123 patients attending antenatal OPD in ï¬rst trimester before 20 weeks of pregnancy were subjected to HbA1c along with other antenatal investigations. These women were subjected to 75gm OGTT at 24-28 weeks and values were correlated. Women with HbA1c > 6.5% or overt diabetes were excluded from study. Maternal and foetal outcomes in patients with and without gestational diabetes mellitus (GDM) were compared.

Results: The prevalence of GDM in our study was 6.95%. Mean HbA1c in the GDM group was 6.46±0.66% while in normal glucose tolerance (NGT) group the mean HbA1c was 4.2±0.9% which was statistically signiï¬cant (p value 0.0001). 63.5% patients were in age range of 26-30 years in GDM group while 62.5% were in the age range of 20-25 years in the NGT group. Mean BMI in GDM group was 22.97±2.68 kg/m2 compared to 23.25±2.59 kg/m2 in NGT group (not statistically signiï¬cant p value 0.68). Incidence of LSCS was 62.5 % in GDM group as compared to 26.1% in NGT group (p value
0.002). There was a strong correlation between HbA1c and OGTT at 0, one and two hours. Based on ROC curve HbA1c cut-off value of 6% has sensitivity of 87.5% and speciï¬city of 96.5% with positive predictive value (PPV) of 63.5% and negative predictive value (NPV) of 99.1% consistent with many studies.

Conclusion: HbA1c can be used as screening test for GDM in early pregnancy along with OGTT as a diagnostic test at 24 to 28 weeks of gestation. Glycosylated hemoglobin (HbA1c) is a simple, single, non-fasting test which also gives us review of blood glucose of previous 8-12 weeks so that patients with pre pregnancy diabetes are also diagnosed early in pregnancy.

Keywords: Normal Glucose Tolerance (NGT); Gestational Diabetes Mellitus (GDM); OGTT; Pregnancy