Evaluation of fasting and random plasma glucose for diagnosis of gestational diabetes.

TLDR: Fasting plasma glucose is a better investigation for the screening of gestational diabetes than plasma glucose post 50-g glucose challenge.

Abstract: OBJECTIVE To compare different cut-off values of fasting and random plasma glucose as a screening test for diagnosis of gestational diabetes in comparison to the 50 grams Glucose Challenge Test (GCT). STUDY DESIGN Comparative, cross-sectional study. PLACE AND DURATION OF STUDY This study was carried out between July 2006 to September 2007 at Departments of Pathology, Obstetrics/Gynaecology and Medicine, PNS Rahat Hospital, Karachi. METHODOLOGY A total of 53 pregnant subjects at 24-28 weeks of pregnancy were selected to undergo random and fasting blood sugar level estimation and 50-g GCT. All the subjects later underwent 100-g OGTT as well. The results were evaluated by both "Carpenter and Coustan criteria" and "NDDG criteria". The results of random plasma glucose random [cut-off: > or = 11.1 mmol/L], fasting plasma glucose (cut-off: > 5.3 mmol/L and > 5.1 mmol/L) and plasma glucose results post 50-g GCT (cut-off: > or =7.8 mmol/L and > or = 7.2 mmol/L) were evaluated against 100-g OGTT results through ROC curve analysis. Finally, various diagnostic parameters including sensitivity, specificity, predictive values, likelihood ratios (LR) and efficiency were evaluated. RESULTS Nineteen subjects were diagnosed to have GDM as per the "Carpenter and Coustan criteria" and 13 met the "NDDG criteria" as per the results of 100-g OGTT. Fasting plasma glucose at was the most efficient investigation at cutoff of 5.1 mmol/L sensitivity=66.66%, specificity=81.25%, PPV=70%, NPV=78.78%, LR+=3.56, LR-=0.41, efficiency=75.47%. At the cut-off value of 5.3 mmol/L, the results had 64% sensitivity, 85.71% specificity, 80% PPV, 72.72% NPV, 4.48 LR+, 0.42 LR-, 75.97% efficiency]. It was followed by plasma glucose post 50-g GCT (53.57% sensitivity at cut-off of > or = 7.2 mmol/L and 54.54% sensitivity at cut-off of > or = 7.8 mmol/L). CONCLUSION Fasting plasma glucose is a better investigation for the screening of gestational diabetes than plasma glucose post 50-g glucose challenge.