Microvascular Complications in Cystic Fibrosis–Related Diabetes

OBJECTIVE—The incidence of cystic fibrosis–related diabetes (CFRD) and the prevalence of diabetic microvascular complications were determined at the University of Minnesota. RESEARCH DESIGN AND METHODS—Cystic fibrosis patients have undergone annual oral glucose tolerance testing since 1990. Database review was performed to determine diabetes duration and the results of annual urine albumin-to-creatinine ratio (Ualb:Cr) screening and dilated retinal exams. In addition, 59 individuals underwent detailed retinopathy, nephropathy, neuropathy, and gastroenterpathy screening. RESULTS—During 1990–2005, 775 patients aged ≥6 years were followed. CFRD was diagnosed by an oral glucose tolerance test or fasting hyperglycemia in 285 subjects (52% female), 64% of whom had fasting hyperglycemia. Most patients with CFRD without fasting hyperglycemia progressed to CFRD with fasting hyperglycemia over time. No subject with CFRD without fasting hyperglycemia had retinopathy or abnormal Ualb:Cr. In CFRD subjects with fasting hyperglycemia and diabetes for ≥10 years, 14% had microalbuminuria and 16% had retinopathy. Autonomic neuropathy and gastrointestinal symptoms each were seen in 52% and somatic abnormalities in 22% of patients with or without fasting hyperglycemia. CONCLUSIONS—Diabetic microvascular complications occur in CFRD, although the prevalence of retinopathy and nephropathy appears to be less than that found in other forms of diabetes. Annual complication screening should occur after known diabetes duration of 5 years in patients with CFRD with fasting hyperglycemia.