Objective This study aimed to determine the glycaemic profile of patients with cystic fibrosis using a continuous glucose monitoring system (CGMS), and to evaluate the associations of glycaemic abnormalities with sex, age, pubertal stage, CFTR gene mutations, nutritional status, lung function, oral glucose tolerance test, glycated haemoglobin concentrations, fasting insulin concentrations, C peptide concentrations and exocrine pancreatic function.

Study design This observational study evaluated CGMS data from 39 patients with cystic fibrosis who were treated at a referral centre. The patients were 10–19.9 years old, and were categorised according to whether they had normal results (27 patients) or glucose intolerance (12 patients) during the oral glucose tolerance test.

Results The maximum interstitial glucose concentration among individuals with normal oral glucose tolerance test results was 174.9±65.1 mg/dL (9.7–3.61 mmol/L), compared with 170.4±40.9 mg/dL (9.46–2.27 mmol/L) among individuals with glucose intolerance. The CGMS revealed that 18 of the 27 patients with normal oral glucose tolerance test results had peak interstitial glucose concentrations of >140 mg/dL (7.8 mmol/L), and that 4 of these individuals had peak levels of >200 mg/dL (11.1 mmol/L). None of the analysed clinical or laboratory characteristics predicted the occurrence of hyperglycaemic peaks on CGMS.

Conclusions The present study revealed that CGMS could detect hyperglycaemia among patients with cystic fibrosis and ‘normal’ oral glucose tolerance test results, and that their clinical and laboratory characteristics were not useful in discerning between patients who did and did not exhibit these excursions.