Comparative study of 50 gram glucose challenge test and 75 gram oral glucose tolerance test in diagnosis of gestational diabetes mellitus in high risk group.

Abstract

Background: Pregnancy is a complex endocrine-metabolic adaptation and diabetogenic condition involving impaired cellular insulin sensitivity, increased β-cell function, and moderate elevation of blood glucose level. The threshold for a positive glucose challenge test (GCT) necessitating further diagnostic testing remains controversial in gestational diabetes mellitus (GDM). Aims & Objective: To find the association of risk factors with GDM, to evaluate the diagnostic value of GCT as compared to oral glucose tolerance test (OGTT) in GDM, and also to determine the optimal cut-off value of GCT with best sensitivity and specificity for the prediction of GDM and also to find the association of GCT between FBS and 2nd hour OGTT glucose level. Material and Methods: The study was conducted at Hanagal Shri Kumareshwara Hospital, Bagalkot, Karnataka, India, from June 2009 to February 2010. 247 pregnant women were selected for the study. Selected women were subjected to screening by GCT. If the blood glucose level was greater than 140 mg/dl, the GCT was considered as positive and these patients were subjected to 75 gm OGTT to confirm the diagnosis of GDM. The diagnosis of GDM was based on WHO criteria. Results: In the present study out of 247 pregnant women selected, 199 women participated, of which 26(13.06%) of the pregnant women were diagnosed to have GDM. Mean age of the study subjects was 24.7±3.51 years. There was a positive association of GDM with age, BMI, glucosuria, polyhydraromnios, obstetrics score, previous GDM, past history of unexplained IUD, family history of DM, recurrent vaginal infection. Area under the curve is 0.994 (p>0.0001) which has best diagnostic accuracy at glucose level of 128 mg/dl, as the best cut off value. Second hour OGTT is more correlated with GCT than FBS. Conclusion: In this ethnic group, the high risk pregnant women for GDM should undergo initial 50 gm. GCT. If GCT value is more than 128 mg/dl, it should be followed by second hour 75 gram OGTT, for the diagnosis of GDM and it reduces the FBS estimation of blood sugar level and an extra prick too.