The 1-h oral glucose tolerance test glucose and insulin values are associated with markers of clinical deterioration in cystic fibrosis.

Abstract

Cystic fibrosis (CF) is associated with the emergence of CF-related diabetes (CFRD). CFRD is associated with increased risk of accelerated weight and/or lung function loss (clinical degradation). Data in the CF pediatric population reported an association between higher 60-min oral glucose tolerance test (OGTT) plasma glucose values and reduced lung function. Our objective was to evaluate the relationship between the 60-min OGTT insulin and glucose values and markers of clinical degradation in adult patients with CF. This study was based on an ongoing observational cohort of CF adult patients (≥18years). All patients underwent a 2-h OGTT with 30-min interval sample measurements. Plasma insulin and glucose levels were measured. Adult patients (N=240) were categorized based on the 60-min OGTT median values of glucose (G60, 11.0mmol/L) and/or insulin (I60, 43.4μU/mL). A negative association was observed between the 60-min OGTT glucose value and pulmonary function (FEV1; P=0.001), whereas 60-min OGTT insulin values were positively associated with BMI (P=0.004). Patients with high G60 values displayed lower FEV1 than patients with low G60 values (P=0.025). Patients with higher I60 values demonstrated higher values of both FEV1 (P=0.022) and BMI (P=0.003) than patients with low I60 values. More importantly, when adjusting for BMI, the difference in FEV1 between both groups no longer existed (P=0.166). Both insulin and glucose values at 60-min OGTT are associated with indicators of clinical degradation in adult patients with CF. Future prospective analyses are essential in establishing the clinical utility of these indicators.