Early Glucose Abnormalities in Cystic Fibrosis Are Preceded by Poor Weight Gain

OBJECTIVE - Progressive beta-cell loss causes catabolism in cystic fibrosis. Existing diagnostic criteria for diabetes were based on microvascular complications rather than on cystic fibrosis-specific outcomes. We aimed to relate glycemic status in cystic fibrosis to weight and lung function changes. RESEARCH DESIGN AND METHODS - We determined peak blood glucose (BG(max)) during oral glucose tolerance tests (OGTTs) with samples every 30 min for 33 consecutive children (aged 10.2-18 years). Twenty-five also agreed to undergo continuous glucose monitoring (CGM) (Medtronic). Outcome measures were change in weight standard deviation score (wtSDS), percent forced expiratory volume in 1 s (%FEV1.), and percent forced vital capacity (%FVC) in the year preceding the OGTT. RESULTS-Dectining wtSDS and %FVC were associated with higher BG(max) (both P = 0.02) and with CGM time >7.8 mmol/l (P = 0,006 and P = 0.02, respectively) but not with BG(120 min). A decline in %FEV1 was related to CGM time >7.8 mmol/l (P = 0.02). Using receiver operating characteristic (ROC) analysis to determine optimal glycemic cutoffs, CGM Lime above 7.8 mmol/l >= 4.5% detected declining wtSDS With 89% sensitivity and 86% Specificity (area under the ROC curve 0,89, P = 0.003). BG(max) >= 8.2 mmol/l gave 87% sensitivity and 70% specificity (0.76, P = 0.02). BG(120 min) did not detect declining wtSDS (0,59, P = 0.41). After exclusion of two patients with BG(120 min) >= 11.1 mmol/l, the decline in wtSDS was worse if BG(max) was >= 8.2 mmol/l (-0.3 +/- 0.4 vs. 0.0 +/- 0.4 for BG(max) <8.2 mmol/l, P = 0.04) or if CGM time above 7.8 mmol/l was >= 4.5% (-0.3 +/- 0.4 vs. 0.1 +/- 0.2 for time <4.5%, P = 0.01). CONCLUSIONS - BG(max) >= 8.2 mmol/l on an OGTT and CGM time above 7.8 mmol/l >= 4.5% are associated with declining wtSDS and lung function in the preceding 12 months.