Postpartum reclassification test in gestational diabetes: can the test be reduced to 1 hour?

Purpose: In gestational diabetes mellitus (GDM), a postpartum oral glucose tolerance test (OGTT) is recommended. However, poor adherence to this procedure has been described, and the time required is one of the reasons. Our aims were to identify predictive factors for abnormal 2-h reclassification OGTT values, including OGTT 1-h glucose, and, if it was a factor, to determine the 1-h cutoff point that best identifies abnormal values at 2 h.

Methods: This was a retrospective study of 769 patients diagnosed with GDM between 2014 and 2019 in a tertiary center. The sample was divided into two groups according to the presence/absence of abnormal 2-h reclassification values, and predictive factors were studied. To determine the 1-h glycemia cutoff point capable of identifying 2-h changes, a ROC curve was drawn and the Youden index was used.

Results: The mean age of included women was 33.6 ± 4.95 years: 70 of them (9.1%) had an abnormal 2-h test result. Women with a history of GDM (OR = 3.41, p = .012) and higher 1-h glycemia value (OR = 1.05, p < .001) had a higher risk of developing an abnormal 2-h test result. One-hour glycemia ≥ 142 mg/dL had a sensitivity of 91.4% and specificity of 75.1% to identify changes in the test at 2 h; area under the curve to predict 2-h changes was 0.90 (CI 95%: 0.86 - 0.93).

Conclusion: Glucose measurement at 1 h predicts alterations at 2 h in the reclassification test with excellent diagnostic accuracy, and the cutoff point of  ≥ 142 mg/dL presents high sensitivity. These findings could serve as a foundation for a possible future redefinition of the OGTT procedure, but further investigation is required.