Screening for cystic fibrosis-related diabetes (CFRD) remains limited by low uptake of the oral glucose tolerance test (OGTT), despite its recommendation in clinical practice. A study published in Diabetes Care evaluated the performance of a nonfasting, 50-g, 1-hour oral glucose challenge test (GCT) as a first-line screening tool for CFRD and pre-CFRD in individuals with cystic fibrosis (CF).

The study included 185 participants aged ≥10 years with CF and no prior diagnosis of diabetes. Participants underwent baseline random plasma glucose (RPG) and random capillary glucose (RCG) testing, followed by an in-clinic GCT to measure 1-hour plasma glucose (GCTpl). Hemoglobin A1C (HbA1c) testing and OGTT were performed on a separate day. Receiver operating characteristic (ROC) curve analysis was used to evaluate diagnostic performance.

Among participants, 94 had normal glucose tolerance, 81 had pre-CFRD, and 10 had CFRD. For detection of pre-CFRD or CFRD, GCTpl demonstrated a ROC-AUC of 0.73 (95% CI 0.65-0.80), which was higher than RPG (0.56, 95% CI 0.48-0.65), RCG (0.55, 95% CI 0.46-0.63), and HbA1c (0.62, 95% CI 0.53-0.67). For detection of CFRD, ROC-AUC was 0.75 (95% CI 0.64-0.86) for GCTpl, compared with 0.64 for RPG and 0.56 for HbA1c.

A GCTpl threshold of 147 mg/dL provided 90% sensitivity and 58% specificity for identifying CFRD. Use of this threshold could reduce the number of OGTTs required by 56%. These findings indicate that GCT may serve as an in-clinic screening approach for CFRD and pre-CFRD in individuals with CF.