Glucose intolerance in cystic fibrosis as a determinant of pulmonary function and clinical status

• CFRD is associated with clinical deterioration.
• We investigated the significance of impaired glucose tolerance (IGT) in CF.
• Patients with IGT had impaired β-cell function and normal insulin sensitivity.
• Patients with IGT had lower BMI-SDS, FEV1 and albumin and higher fibrinogen.
• IGT in CF patients is associated with clinical deterioration.

BackgroundCystic fibrosis related diabetes (CFRD) is associated with a decrease in pulmonary function and nutritional status. We investigated the clinical significance of impaired glucose tolerance (IGT) in cystic fibrosis (CF) patients.MethodsFifty-five CF patients (aged 22.8 ± 9.2 years, 29 males, mean FEV1 67.9 ± 22% predicted, mean BMI-SDS −0.23 ± 1.1) underwent a 2-h Oral Glucose Tolerance Test (OGTT) with 30-min interval measurements of glucose and insulin. Additional clinical and laboratory data were obtained from the medical charts.ResultsThirty-eight participants (69%) had normal glucose tolerance (NGT), 13 (23.7%) had IGT, and 4 (7.3%) had newly diagnosed CFRD. Compared to patients with NGT, patients with IGT had significantly lower BMI-SDS (−1.1 ± 0.8 vs. 0.1 ± 1.1, p < 0.001), mean FEV1 (57 ± 19 vs. 74 ± 21% predicted, p < 0.01), and albumin (3.9 ± 0.3 vs. 4.3 ± 0.2 g/dl, p = 0.004), and higher fibrinogen (376 ± 56 vs. 327 ± 48 g/dl, p = 0.02). Patients with IGT had impaired β-cell function, with reduced first phase insulin secretion, a delayed insulin peak, and significantly lower total insulin secretion, HOMA-%B and insulinogenic index. Seven patients had HbA1c in the “diabetic” range (≥6.5%; 47.5 mmol/mol), however, HbA1c was not a sensitive or specific marker of glucose tolerance status.ConclusionsIGT in CF patients is associated with increased inflammation and decreased nutritional status and pulmonary function.