Cystic fibrosis-related diabetes (CFRD) affects a substantial proportion of adults with Cystic Fibrosis, yet screening with the recommended oral glucose tolerance test (OGTT) remains underused. A study published in Diabetes Care found that a nonfasting 50-g, 1-hour oral glucose challenge test (GCT) may offer a practical first-line approach for identifying CFRD and pre-CFRD.
The study enrolled 185 participants aged 10 years or older with cystic fibrosis and no known diabetes. Baseline random plasma glucose (RPG) and random capillary glucose (RCG) were measured, followed by an in-clinic GCT with 1-hour plasma glucose collection (GCTpl). Hemoglobin A1c (HbA1c) testing and OGTT were then completed on a separate day. Receiver operating characteristic analyses assessed test performance for CFRD and pre-CFRD detection.
Among participants, 94 had normal glucose tolerance, 81 had pre-CFRD, and 10 had CFRD. For detecting pre-CFRD or CFRD, GCTpl achieved a ROC-AUC of 0.73 (95% CI 0.65-0.80), which exceeded RPG at 0.56 (95% CI 0.48-0.65; P = 0.003), RCG at 0.55 (95% CI 0.46-0.63; P = 0.002), and HbA1c at 0.62 (95% CI 0.53-0.67; P = 0.02).
For CFRD detection alone, ROC-AUC was 0.75 (95% CI 0.64-0.86) with 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 CFRD and could reduce OGTT testing by 56%.
These findings suggest that the 1-hour GCT may help expand opportunistic in-clinic screening for CFRD while reserving OGTT for higher-risk individuals.
