Diagnostic effectiveness of 75 g oral glucose tolerance test for gestational diabetes in India based on the International Association of the Diabetes and Pregnancy Study Groups guidelines

Abstract

Background To determine the diagnostic effectiveness of the fasting and one-hour plasma glucose levels for gestational diabetes (GDM) based on International Association of the Diabetes and Pregnancy Study Groups (IADPSG) criteria. Methods A Cross-sectional study that included 2348 pregnant women booked for antenatal care in 2011 at a tertiary care perinatal institute. Pregnant women underwent a 75 g oral glucose tolerance test (OGTT) between 24 and 28 weeks of gestation. Outcome measures include the incidence of GDM based on the IADPSG criteria and the diagnostic effectiveness of the recommended fasting and one-hour plasma glucose cut-off if used in isolation. Results The incidence of GDM was 21.81% ( n = 520, 95% CI: 20.15, 23.57) with the IADPSG criteria. A fasting plasma glucose cut-off 92 mg/dL, in isolation, correctly classified 87.16% of GDM, with a specificity of 96.08%, clinically significant positive likelihood ratio (14.08) and a post-test probability of 79.71%. The one-hour 75 g test, in isolation, correctly classified 85.74% of GDM, had specificity of 99.68% and clinically significant positive likelihood ratio (111.12) and post-test probability of 96.87%. The application of the World Health Organization criteria would misclassify 11.91% (95% CI: 10.66, 13.26) of GDM as normal. Conclusions Additional testing of plasma glucose levels can be avoided for 18.25% ( n = 435, 95% CI: 16.73, 19.84) if the IADPSG diagnostic criteria for GDM are applied with exit on a positive fasting or one-hour test result.