Dysglycemia in the cystic fibrosis (CF) population is widespread and screening via oral glucose tolerance tests (OGTT) can be burdensome. Our primary aim was to investigate 1,5-anhydroglucitol (1,5AG), fructosamine (FA), glycated albumin (%GA), and hemoglobin A1c (HbA1c) as screening tests for cystic fibrosis-related prediabetes (CFPD) and cystic fibrosis-related diabetes (CFRD) in youth with CF as defined by the OGTT 2-hour glucose (2hG). Our secondary aim was to determine if alternate screening tests can identify those with better or worse lung function (forced expiratory volume in 1 second, FEV1%; forced vital capacity, FVC%). Youth 10-18 years with CF had 1,5AG, FA, %GA, HbA1c, and a 2 hour OGTT collected during a single study visit. Pearson’s correlation coefficient determined the correlation between all 4 glycemic estimates and 2hG. Receiver Operative Characteristic (ROC) curves were generated. The Youden Index determined optimal cut points for predicting CFPD (2hG≥140-200 mg/dL) and CFRD (2hG≥200 mg/dL). Lung function measures above and below these cutpoints were compared. Fifty-eight youth with CF participated (2hG<140, n=31; CFPD, n=17; CFRD, n=10; mean age 14±3.5 years, 43% male, BMI z-score 0.0±0.8, FEV1% 90±15.0, FVC% 99±14.1). FA, %GA, and HbA1c correlated with 2hG (p-<0.05). ROC area under the curves (ROC-AUCs) for all 4 alternate markers were low for both CFPD (0.53-0.67) and CFRD (0.56-0.66). HbA1c had the highest ROC-AUC of 0.66 (95% CI: 0.47-0.84) for identifying CFRD and 0.67 (95% CI: 0.53-0.8) for CFPD. When lung function was compared stratifying above and below the Youden cutpoint for CFRD, only HbA1c identified significant differences in FVC% (105% vs. 96%, p=0.02); FEV1% was not statistically significant (96% vs. 88%, p=0.06). All 4 alternate markers had poor diagnostic accuracy for identifying CFRD by 2hG, although HbA1c may be useful in detecting CFPD and in stratifying individuals with CF by lung function.


K.L. Tommerdahl: None. J.T. Brinton: None. T.B. Vigers: None. K.J. Nadeau: None. P. Zeitler: Consultant; Self; Daiichi Sankyo Company, Limited, Merck & Co., Inc., Eli Lilly and Company, Takeda Development Center Americas, Inc., Boehringer Ingelheim GmbH. C.L. Chan: None.

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