Elevation of One Hour Plasma Glucose During Oral Glucose Tolerance Testing

Objectives: In cystic fibrosis (CF) patients, elevations in 1 hr plasma glucose (PG1) during a 75 g oral glucose tolerance test are common, but of unclear long-term clinical relevance. Thus, we examined associations of PG1 with percent-predicted forced expiratory volume in 1 sec (FEV1% predicted), CF exacerbations, and CF related diabetes (CFRD) development. Study Design: We conducted a retrospective cohort study of 80 pediatric patients with CF (43 males) followed over 5 years in a single CF center. We considered the association between elevated versus normal PG1 (greater vs. no greater than 160 mg/dl) and linear changes in FEV1% predicted over time for males and female, as well as the odds of a CF exacerbation and the odds of developing CFRD. Results: No significant difference in FEV1% predicted between normal versus elevated PG1 was found at baseline, or over time in males or females. However, males with elevated PG1 tended to have worse FEV1% predicted over time than those with normal PG1 (reduction of 0.9 FEV1% predicted/year, 95% CI: -2.5, 0.6). Subjects with PG1 > 160 mg/dl were more likely to develop CFRD (OR 4.5, 95% CI: 1.7, 18.7, P = 0.04) but CF exacerbation risk was similar in both groups. Conclusion: The risk of CFRD increases with PG1 > 160 mg/dl. No statistically significant evidence of an association between elevated PG1 and pulmonary function was found, yet our results do not exclude the possibility that in males, elevated PG1 may signal adverse changes in FEV1% predicted over time. This possibility requires further study with a larger sample size. (C) 2015 Wiley Periodicals, Inc.