Retrospective review of GCT cutoff value based on pre-pregnancy BMI class in patients with GDM.

OBJECTIVES: To determine the optimal glucose challenge test (GCT) cutoff value for the screening of gestational diabetes mellitus (GDM) based on pre-pregnancy BMI. METHODS: An-IRB approved retrospective cohort analysis of singleton pregnancies at a large tertiary healthcare center from January 2004 to December 2020 was performed. The first GCT value completed between 20 and 32 weeks was used. Using a receiver operator curve (ROC), we sought to determine the optimal GCT cutoff value for each BMI category that would predict the development of GDM. Youden Index was used to determine optimal cut-point of GCT values for each BMI class. RESULTS: A total of 23,550 patients with a GCT value were identified. Of those, 1,676 (7.1%) were diagnosed with GDM. 513 (30.6%) with normal BMI, 449 (26.8%) overweight, 347 (20.7%) class I obese, 210 (12.5%) class II obese, and 157 (9.4%) class III obese patients were diagnosed with GDM. Gestational diabetes was predicted at GCT cutoff value of 130 mg/dL with an area under the curve (AUC) of 0.92 (BMI <25), 131 mg/dL with an AUC of 0.92 (overweight BMI), 131 mg/dL with an AUC of 0.89 (class I BMI), 133 mg/dL with an AUC of 0.88 (class II BMI), and 131 mg/dL with an AUC of 0.88 (class III BMI). CONCLUSIONS: AUC ranged from 0.88 to 0.92 with 93% or greater sensitivity for GCT cutoff value across each of the BMI categories. The findings support a GCT cutoff value of 130 mg/dL for GDM screening regardless of BMI.