Oral glucose tolerance test and continuous glucose monitoring to assess diabetes development in cystic fibrosis patients

Abstract

IntroductionPatients with cystic fibrosis (CF) undergo a slow and progressive process toward diabetes. Oral glucose tolerance test (OGTT) is recommended to diagnose impaired glucose levels in these patients. Continuous glucose monitoring (CGM) measures glucose profiles under real-life conditions. ObjectiveTo compare OGTT and CGM results in CF patients. MethodsPaired OGTT and 6-day CGM profiles (146.2±9.1h/patient) were performed in 30 CF patients aged 10–18 years. ResultsAccording to OGTT, 14 patients had normal glucose tolerance (NGT), 14 abnormal glucose tolerance (AGT), and two cystic fibrosis-related diabetes (CFRD). In 27 patients (13 NGT, 13 AGT, 1 CFRD), CGM showed glucose values ranging from 140 to 200mg/dL during similar monitoring times (2%–14% with NGT, 1%–16.9% with AGT, and 3% with CFRD). Glucose peak levels ≥200mg/dL were seen in seven patients (3 NGT, 3 AGT, 1 CFRD).According to CGM, two patients had all glucose values under 140mg/dL (1 NGT, 1 AGT). Seventeen patients had glucose levels ranging from 140 to 200mg/dL (10 NGT, 6 AGT, 1 CFRD). Ten patients (3 NGT, 7 AGT) had glucose values ≥200mg/dL for ≤1% of the monitoring time and one (CFRD) for >1% of the monitoring time. ConclusionsOGTT results did not agree with those of the CGM. CGM allows for diagnosis of glucose changes not detected by OGTT. Such changes may contribute to optimize pre-diabetes management in CF patients.