Efficacy of 50g Glucose Challenge Test as a Screening Tool for Gestational Diabetes Mellitus

Abstract

Objective: To evaluate the validity of 50 g oral Glucose Challenge Test as a screening tool for GDM in our population. Materials and Methods: This cross sectional study was carried out in Obstetrical clinic, Combine Military Hospital (CMH) Lahore. 100 women carrying singleton pregnancy between 20-35 years of age, booked in first trimester were included while patients with risk factor of GDM or with established type I or II DM were excluded from study. 50 g GCT was administered to patients between 24-28 weeks of gestation after informed consent. Venous plasma glucose levels after 1 hour of glucose load, were taken, using 140 mg/dl as a cut off value. Regardless of results of screening, all patients were tested with 100 g OGTT as a “gold standard” of diagnosis of GDM.. Validity of 50g GCT was calculated for sensitivity, specificity, positive and negative predictive value. Data was analysed by SPSS version 16. Results: Out of 100 patients, 19% were screen positive and 81% screened negative with 50g GCT. With100 g OGTT, true positive were 10 out of 19(52.6%) screen positive, and false positive were 9 out of 19(47.4%) screen positive. False negative were 3 out of 81(3.7%) screen negative, whereas true negative were 78 out of 81(96.3%) screen negative. Validity of 50 g GCT has been calculated to be having sensitivity of 76.92%, specificity of 89.6%, positive predictive value of 52.6% and negative predictive value of 96.2%. Conclusion: 50 g GCT is an effective screening tool for GDM between 24-28 weeks of gestation with adequate sensitivity and specificity