Can continuous glucose monitoring predict cystic fibrosis-related diabetes and worse clinical outcome?

OBJECTIVE: To determine whether abnormal continuous glucose monitoring (CGM) readings (hypoglycemia/hyperglycemia) can predict the onset of cystic fibrosis-related diabetes (CFRD) and/or clinical impairment (decline in BMI and/or FEV(1)) in pediatric patients with cystic fibrosis (CF). METHODS: This was a longitudinal prospective cohort study involving CF patients without diabetes at baseline. The mean follow-up period was 3.1 years. The patients underwent 3-day CGM, performed oral glucose tolerance test (OGTT), and had FEV(1) and BMI determined at baseline. OGTT, FEV(1,) and BMI were reassessed at the end of the follow-up period. RESULTS: Thirty-nine CF patients (10-19 years of age) had valid CGM readings at baseline, and 34 completed the follow-up period (mean = 3.1 ± 0.5 years). None of the study variables predicted progression to CFRD or were associated with hypoglycemic events. CGM could detect glucose abnormalities not revealed by OGTT. Patients with glucose levels ≥ 140 mg/dL, as compared with those with lower levels, on CGM showed lower BMI values and z-scores at baseline-17.30 ± 3.91 kg/m(2) vs. 19.42 ± 2.07 kg/m(2); p = 0.043; and −1.55 ± 1.68 vs. −0.17 ± 0.88; p = 0.02, respectively-and at the end of follow-up-17.88 ± 3.63 kg/m(2) vs. 19.95 ± 2.56 kg/m(2); p = 0.039; and −1.65 ± 1.55 vs. −0.42 ± 1.08; p = 0.039. When comparing patients with and without CFRD, the former were found to have worse FEV(1) (in % of predicted)-22.67 ± 5.03 vs. 59.58 ± 28.92; p = 0.041-and a greater decline in FEV(1) (−36.00 ± 23.52 vs. −8.13 ± 17.18; p = 0.041) at the end of follow-up. CONCLUSIONS: CGM was able to identify glucose abnormalities not detected by OGTT that were related to early-stage decreases in BMI. CGM was ineffective in predicting the onset of diabetes in this CF population. Different diagnostic criteria for diabetes may be required for individuals with CF.