Diagnostic accuracy of 50 g glucose challenge test for screening of the gestational diabetes mellitus using 75 g oral glucose tolerance test as reference standard

Abstract

Background: Gestational diabetes mellitus (GDM) is a common causative factor of grave maternal and fetal consequences. Prompt and precise diagnosis of GDM can aid in lessening the likelihood of these unfavorable outcomes.

Objective: To find the diagnostic accuracy of 50 g GCT (glucose challenge test) for detecting GDM, using 75 g OGTT (oral glucose tolerance test) as the reference standard and to find complications of GDM were also reported.

Methodology: A diagnostic cross-sectional study was executed at the outdoor patient department of gynecology unit, Lahore General Hospital, Lahore. It comprised of 285 pregnant females aged ≥ 18 years who were screened for GDM. All participants undertook 50 g GCT, followed by 75 g OGTT. Result was considered true positive if GDM was reported on both tests. A 2x2 table was made to estimate the sensitivity and specificity, positive predictive value (PPV) and negative predictive value (NPV) and diagnostic accuracy of GCT using OGTT as gold standard.

Results: Mean age of patients was 26.28±4.183 years. According to GCT, 39 (13.68%) cases were positive for GDM. On the other hand, 42 (14.74%) tested positive for GDM using 75 g OGTT. We found Sensitivity = 85.71%, Specificity = 98.77% of 50 g GCT and PPV = 92.31 % NPV = 97.56% and overall diagnostic accuracy was found as 96.84%. A total of 86(30.17%) participants reported gestational hypertension whereas Hydramnios was reported in 26 (9.12%) participants. 94(32.98%) patients underwent cesarean section due to cephalopelvic disproportion. Macrosomia, shoulder dystocia and neonatal hypoglycemia was reported in 36(12.63%), 14(4.91%) and 84(29.47%) cases, respectively.

Conclusion: 50g GCT provided significantly high sensitivity and specficity for diagnosing GDM. As it is a cost-effective and provides reasonably accurate results, it can be used as an alternate to 75 g OGTT. This could aid in minimizing the maternal and fetal consequences by timely identification of the condition.