Glucose Tolerance and Its Clinical Impact in Children and Adolescents With Cystic Fibrosis

Patients with cystic fibrosis (CF) with progressing disease are developing a glucose tolerance which resembles the metabolic state of a diabetic patient because of increasing impairment of endocrine pancreatic function. The prevalence of this diabetic metabolic state is increasing with age, reaching around 20% at the age of 20 years.

Over the last decade, research has already highlighted the negative influence of cystic fibrosis related diabetes (CFRD) on morbidity and mortality after the diagnosis of this condition.

As the deterioration in nutritional status and lung function can already be noticed 2-6 years before the onset of CFRD, the importance of early diagnosis in glucose abnormalities and its treatment therefore is crucial.

The currently used method to evaluate altered glucose metabolism in patients with CF is an annual oral glucose tolerance test (OGTT) with the glucose value after 120 min after oral ingestion of glucose-fluid as reference. This method may detect CFRD much later than we see deterioration of lung function and weight loss. This deterioration and the mortality in CF is related to CFRD.

An alternative diagnostic tool that has gained increasing attention and that is already routinely used in pediatric patients with diabetes mellitus type I is the continuous glucose monitoring system (CGMS) which was shown to be much more sensitive in detecting glucose abnormalities. To assess pancreatic endocrine dysfunction - the pathophysiologic cause for glucose intolerance - intravenous glucose tolerance testing (IVGTT) is the gold standard.