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.