GLUCOSE-TOLERANCE IN PATIENTS WITH CYSTIC-FIBROSIS - 5-YEAR PROSPECTIVE-STUDY

Objectives-To study prevalence and incidence of diabetes mellitus in p atients with cystic fibrosis. Design-Five year prospective study with annual oral glucose tolerance tests. Setting-CF Center Copenhagen, Den mark. Subjects-191 patients with cystic fibrosis aged above 2 years. M ain outcome measures-Glucose tolerance, plasma glucose concentrations after fasting and after glucose loading, and haemoglobin A(1c) levels. Results-Prevalence of diabetes increased from 11% (n=21) to 24% (n=46 ) during study, with annual age dependent incidence of 4-9%. Diabetes was diagnosed at median age of 21 (range 3-40). At diagnosis of diabet es, symptoms of hyperglycaemia were present in 33% of patients, fastin g hyperglycaemia (greater than or equal to 7.8 mmol/l was seen in 16%, and increased haemoglobin A(1c) levels (>6.4%) were seen in 16%. Impa ired glucose tolerance implied higher risk for development of diabetes than normal glucose tolerance (odds ratio 5.6). In 58% of cases with impaired glucose tolerance, however, glucose tolerance was normal at n ext annual test. Normal glucose tolerance was found in only 37% of pat ients at all five tests. Within this group of patients, median plasma glucose concentrations after fasting and after glucose loading and hae moglobin A(1c) levels increased by 6-8% during study. Conclusions-Prev alence and incidence of diabetes in cystic fibrosis patients was high and increased with age. Since hyperglycaemic symptoms, fasting hypergl ycaemia, and increased levels of glycated haemoglobin did not reliably identify diabetes mellitus, we recommend annual oral glucose toleranc e tests in all cystic fibrosis patients aged over 10 years.