Establishing novel diagnostic criteria for the glucose tolerance test for the diagnosis of gestational diabetes and gestational hyperglycemia

AbstractObjectiveTo establish diagnostic criteria for the 75‐g 2‐h glucose tolerance test (GTT) to diagnose gestational diabetes and define the clinical entity of gestational hyperglycemia.MethodsA retrospective analysis was performed of the results from 500 patients who had a 75‐g 1‐h glucose challenge test (GCT) in early pregnancy as part of a two‐step approach to screening and testing for gestational diabetes. The selected cohort was considered to have normal islet β‐cell function, and upper glycemic levels of normal glucose tolerance in the third trimester were statistically calculated, taking the cutoff threshold values to be the diagnostic criteria for the 75‐g 2‐h GTT. Gestational hyperglycemia was diagnosed from the false‐positive GCT result when ≥8.0 mmol/L (144 mg/dL).ResultsThe diagnostic criteria for the 75‐g 2‐h GTT were calculated as follows: fasting plasma glucose ≥5.4 mmol/L (97 mg/dL); 1‐h plasma glucose ≥10.5 mmol/L (189 mg/dL); and 2‐h plasma glucose ≥8.4 mmol/L (151 mg/dL). The new criteria confirmed a prevalence of gestational diabetes of 11.1% and gestational hyperglycemia of 13.6% in the study population.ConclusionNovel diagnostic criteria for the 75‐g 2‐h GTT were established by statistical analysis. This resulted in a more acceptable prevalence of gestational diabetes in our community and the false‐positive GCT allowed the detection of gestational hyperglycemia.