Glycated haemoglobin versus oral glucose tolerance test in screening for gestational diabetes mellitus

Background: Glycated haemoglobin (HbA1c) has been documented as an easier, useful tool in diagnosis of diabetes and can be considered as a screening tool in GDM as compared to oral glucose tolerance test (OGTT) which has practical constraints like long waiting period in fasting, too many pricks and non-compliance to glucose load solution. The objective of the study was to find out the utility of HbA1c as a diagnostic tool when compared with OGTT in screening of GDM.Methods: A retrospective study was conducted at Sri Venketeswaraa Medical College, Hospital and Research Center, Puducherry including 500 antenatal women attending to the Department of Obstetrics and Gynaecology for their ante-natal checkup during the period from August 2016 to April 2018. HbA1c levels were estimated and ROC curve analysis was done to estimate sensitivity and specificity against gold standard OGTT.Results: The HbA1c levels among the study subjects varied from 4.3% to 8.2%. The mean HbA1c levels among those diagnosed as GDM by gold standard OGTT was 5.82±1.1% and among those without GDM was 5.13±0.7%. The area under the ROC curve was 0.773 (95% CI 0.732–0.814). An HbA1c cut-off value of ≥5.91% had sensitivity of 34.6% and Specificity of 98.2% in diagnosing GDM. An HbA1c cut-off value of ≥5.32% had sensitivity of 84.8% and specificity of 60.1% in diagnosing GDM.Conclusions: HbA1c levels cannot substitute OGTT in diagnosis of GDM. A higher specific cut-off HbA1c value of ≥5.95% is diagnostic of GDM