Cystic fibrosis-related diabetes (CFRD) may be diagnosed by fasting blood glucose ≥ 7.0 mmol/L and/or glucose ≥ 11.1 mmol/L following oral glucose tolerance test (OGTT). We compared the role of fasting and stimulated glucose for diagnosis of CFRD.

We performed a cross-sectional review of the prevalence of fasting glycemic abnormalities and Kaplan-Meier survival analysis of risk of progression to CFRD according to baseline fasting glucose in the prospective Montreal Cystic Fibrosis Cohort.

Isolated fasting hyperglycemia was detected in only 8% of participants at study onset. Eighty percent of subjects had isolated post-challenge hyperglycemia on their first OGTT meeting criteria for CFRD. Kaplan Meier survival analysis demonstrated that impaired fasting glucose (IFG) alone is not a risk factor for CFRD. Subjects with combined IFG and impaired glucose tolerance at baseline (IGT) had the highest risk of progression to CFRD.

Post-prandial elevations in blood glucose are more common at diagnosis of CFRD. While IGT is a significant risk factor for CFRD, IFG alone is uncommon and does not increase the risk of CFRD. Patients with both IGT and IFG have the highest risk of CFRD.