Diagnosis of gestational diabetes mellitus: is it time for a new critical value?

To identify the value for the 1-hour glucose tolerance test (GTT) that would maintain 100%, 90% and 75% sensitivity for identifying abnormal 3-hour GTT results in prenatal patients from an East Coast, urban, university hospital setting.

Two hundred forty-two women who underwent the 3-hour GTT during pregnancy between January 1, 2004, and February 1, 2005, at a university hospital laboratory and private laboratories were included. The preceding 1-hour GTT results were obtained from these women, and a receiver operating characteristic (ROC) curve was constructed to identify a 1-hour GTT cutoff value that would maintain 100%, 90% and 75% sensitivity. A subgroup analysis was performed of patients of Asian ethnicity. This study was approved by the institutional review board.

To maintain 100% sensitivity of the 1-hour GTT in predicting an abnormal 3-hour GTT, the 1-hour GTT cutoff value could be raised to 144 mg/dL in our population. For 90% and 75% sensitivities, the values were 150 and 156 mg/dL, respectively. There was no clinically significant difference in ROC curve evaluation between Asian and non-Asian groups.

Raising the current level of 135 mg/dL for a 1-hour GTT to potentially decrease the need for the 3-hour GTT should be considered if larger patient series yield findings similar to those in our population.