Screening for gestational diabetes mellitus

Abstract

INTRODUCTION: Much confusion surrounds screening for glucose intolerance during pregnancy. METHOD: Pregnant women registered for ANC by PHMs in the Homagama DDHS area between 01/04/2003 - 30/09/ 2003 (n= 853), were subjected to selected screening tests: random urinary Benedict's test, random urinary dipstick test, post prandial urinary Benedict's test, post prandial urinary dipstick test, fasting capillary blood glucose (cut off = 74mg/dl), presence of risk factors (American Diabetic Association), 2h post prandial capillary blood glucose (cut off= 130 mg/dl) and OGTT at POA of 24-28 weeks. All screening tests were validated against the OGTT (2 hour 75g Gold standard). Capillary whole blood glucose estimation was by Accutrend glucometer and results interpreted according to WHO criteria. (Post prandial = 2h post 75g glucose) RESULTS: Validity of screening tests to detect gestational diabetes mellitus was as follow: (PLEASE AQUIRE THE FULL PAPERS FOR THE DATA TABLE) Since WHO and ADA do not advocate using post prandial blood sugar test alone to diagnose GDM, we calculated the appropriate cut off values by the ROC curve method. The calculated cut off value was 130mg/dl. CONCLUSIONS: 1) The current National MCH system screening tool for GDM (random urine Benedict's test) validated against the OGTT has a low sensitivity and a high likelihood of being false positive, thus making it an unacceptable screening tool. 2) Testing post prandial urine with semi quantitative enzyme based test strips (Dipstick) has moderate sensitivity but a high false positive rate. 3) FBS as a screening test for GDM is unsuitable due to a high false positive rate. 4) The presence of risk factors used as a selection criterion to screen for GDM has high sensitivity, but a high false positive rate. 5) Capillary 2h post prandial test (cut off 130 mg/dl) has a high sensitivity and specificity, thus the most valid screening tool. RECOMMENDATIONS: In-depth cost analysis must be carried out on 2h PPBS versus universal screening with OGTT and/or selection for OGTT based on risk factors.