Assessment of the Utility of Hba1c Compared to Oral Glucose Tolerance Test in Diagnosis of Gestational Diabetes Mellitus at Kenyatta National Hospital

Abstract

Background information: GDM stands for gestational diabetes mellitus, which is diabetes diagnosed during the second and third trimesters of pregnancy and is not obviously type 1 or type 2 diabetes prior to pregnancy. During pregnancy and after birth, it has negative consequences for both the mother and the fetus. The Oral Glucose Tolerance Test is the gold standard test for diagnosing GDM but is time consuming and expensive. It involves fasting, ingestion of a high concentrated glucose solution and multiple invasive sample collection. Glycosylated hemoglobin (HbA1c) test is a single, simple, random, non- fasting, noninvasive, time saving and economical test that can be performed instead of OGTT, however the cut off value for pregnant mothers has not been established. Objectives: To determine the utility of glycosylated hemoglobin compared to oral glucose tolerance tests in diagnosis of GDM (OGTT, IADPSG). Materials and Methods: Descriptive cross-sectional study was employed among pregnant women (139) at 24-28 weeks gestational period, receiving ante-natal care services at Kenyatta National Hospital. Oral Glucose Tolerance Test (IADPSG) and HbA1c tests (Clover A1cTM analyzer system) were performed. The Receiver Operating Characteristic (ROC) curve was prepared. The area under the curve (AUC) was calculated. The performance of HbA1c for detection of GDM were evaluated against the gold standard (OGTT). Results: Between March and July 2020, 139 participants were enrolled. Gestational age was 24 – 28 weeks. The prevalence of GDM was as follows:- 72(51.8%) using OGTT (IADPSG criteria), 9 (6.47%) using HbA1c cut off of > 6.5%, 113(81.29%) using HbA1c cut off of >4.95% and 101 ( 77.8%) using HbA1c cut off of 5.1%.The HbA1c cut off of >6.5% had low sensitivity of 11.2% while the cut-off of >4.95% had a high sensitivity of 88.9%. Both had low PPV (88.9%, 56.6%) and NPV (51.5%, 69.2%) respectively. ROC generated an AUC of 0.598 and cutoff of >4.95%. There was a significant difference between the two variables with p= 0.003 which is less than 0.05.There was an agreement between results generated by IADPSG and WHO 2013, OGTT criteria. Conclusion: It was found out that HbA1c cannot be used as a diagnostic tool for GDM because the cut off value of > 6.5% had low sensitivity while the cut off value of >4.95% generated by the ROC is too low and is within the reference range for pregnant women.