Impaired Fasting Glucose in Cystic Fibrosis

OBJECTIVE While glucose tolerance abnormalities are common in cystic fibrosis (CF), impaired fasting glucose (IFG) has scarcely been explored. No studies have examined the relation between IFG and clinical status. RESEARCH DESIGN AND METHODS Data were retrieved from the University of Minnesota CF database on oral glucose tolerance tests (OGTTs) performed in 1996-2005. Subjects were identified as normal glucose tolerance (NGT), impaired glucose tolerance (IGT), or CF-related diabetes without fasting hyperglycemia (CFRD FH-). Patients with fasting hyperglycemia were excluded. The presence of IFG was assessed within each category. In a separate case-control cohort study, subjects with IFG were matched to CF control subjects by age, sex, and OGTT class to explore outcomes. RESULTS For the total population (n = 310), the prevalence of IFG was 22%, and by OGTT class was NGT 14%, IGT 31%, CFRD FH- 53%. Within the cohort study, mortality was significantly reduced in IFG (two vs. nine deaths, odds ratio [OR] = 0.2 [95% CI 0.04-0.9]). IFG did not confer increased risk of progression to diabetes (OR 0.66 [0.29-1.48]). Lung function was better in pediatric IFG subjects with IGT and not significantly worse in adults with IGT or adults and children with NGT and CFRD FH-. BMI was not significantly different in IFG subjects versus control subjects. CONCLUSIONS Contrary to expectations in patients with CF, IFG appeared to be associated with improved survival and was not associated with worse nutritional or pulmonary status or increased progression to fasting hyperglycemia.