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

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Dr. Rekha Jain
Dr. Manisha Sharma
Dr. Harsh Vardhan Singh
Dr. Nayanisiri
Dr. Rajiv Ranjan

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 find the usefulness of Glycosylated hemoglobin (HbA1c) as a screening method for GDM in first 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 first 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 significant (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 significant 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 specificity 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

Published May 22, 2020

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