Combined Indeterminate and Impaired Glucose Tolerance Is a Novel Group at High Risk of Cystic Fibrosis-Related Diabetes

Background Indeterminate glycemia (INDET) and impaired glucose tolerance (IGT) are independently associated with cystic fibrosis-related diabetes (CFRD) risk. We determined whether patients meeting both criteria have increased risk of diabetes in 2 separate adult cohorts. Methods The Montreal Cystic Fibrosis Cohort (MCFC; n = 293 baseline and 198 for prospective analysis excluding subjects identified with incident CFRD at baseline) and the Lyon cystic fibrosis cohort [Determination of the Predictive Factors in the Reversibility or the Aggravation in the Disorders of the Glucose Metabolism in Cystic Fibrosis Patients (DIAMUCO); n = 144/105] are prospective observational cohorts. Results In the MCFC and DIAMUCO cohorts, mean age was 25.5 ± 7.7 and 25.0 ± 8.6 years; body mass index, 21.7 ± 3.0 and 20.2 ± 2.2 kg/m2; percentage of forced expiratory volume expired in 1 sec, 73.2 ± 22.1 and 62.5 ± 21.9; and follow-up, 6.9 ± 3.8 and 2.4 ± 1.2 years, respectively. In the MCFC cohort, the IGT only and combined INDET and IGT (INDET + IGT) groups had greater risk of CFRD (P = 0.0109). In the DIAMUCO cohort, there was lower diabetes-free survival in the INDET + IGT group (P = 0.0105). In both cohorts, CFRD risk ranged from 17% in normal glucose tolerance patients up to 42% to 56% in patients with INDET + IGT. Conclusion Patients who meet combined criteria have a higher risk of developing diabetes probably justifying closer follow-up.