Comparison of Diagnostic Accuracy of Non-fasting DIPSI and HbA1c with Fasting WHO Criteria for Diagnosis of Gestational Diabetes Mellitus

Background: To compare diagnostic accuracy of non-fasting DIPSI and HbA1c with fasting WHO 1999 as gold standard for diagnosis of gestational diabetes mellitus (GDM). Methods: Pregnant women attending antenatal clinic underwent a 2-h 75-gm GCT in non-fasting state (DIPSI). HbA1c was also determined at the same sitting. A 2-h 75-gm GCT was repeated for all women after 72 h in a fasting state (WHO criteria). GDM was diagnosed if plasma glucose was ≥140 mg/dl by either test or if HbA1C ≥6%. Results: Of the 800 women evaluated, 51 were diagnosed as GDM by WHO criteria, 63 by DIPSI, and 40 by HbA1c. The sensitivity of DIPSI test with respect to WHO 1999 was 98.04% and specificity 98.26%. The diagnostic accuracy was 98.25%. The area under the ROC curve for DIPSI was 0.988 ( p < 0.001) (95% confidence interval: 0.960-1.000). The sensitivity of HbA1c with respect to WHO GTT was 47.06%, specificity 97.86%, and diagnostic accuracy 94.63%. The ROC curve between WHO GTT and HbA1c covered an area of 0.805 ( p < 0.01) (95% confidence interval: 0.731-0.879). Conclusions: Non-fasting DIPSI criteria had high diagnostic accuracy compared to gold-standard WHO GTT and can be an effective and practical alternative to the latter. HbA1c had a low sensitivity although the specificity was good and therefore is not a suitable test for screening GDM.