The 1-h oral glucose tolerance test glucose and insulin values are associated with markers of clinical deterioration in cystic fibrosis
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 (≥18 years). 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, 11.0 mmol/L) and/or insulin (I60, 43.4 μU/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.
KeywordsCystic fibrosis-related diabetes Oral glucose tolerance test Insulin Glucose Pulmonary function Body mass index
Oral glucose tolerance test
OGTT plasma glucose values at 60 and 120 min
OGTT plasma insulin values at 0, 60 and 120 min
Centre Hospitalier de l’Université de Montréal
Area under the curve
Indeterminate glucose tolerance
We thank the CF and diabetes clinic nurses for OGTT coordination.
Compliance with Ethical Standards
Conflict of interest
The authors declare that they have no conflict of interest.
This study is supported by the J-A DeSève chair for clinical research to RRL and by an operating team grant from the Canadian Cystic Fibrosis Foundation (No. 18608) to RRL and YB. AC holds the Michel Bélanger PhD scholarship from the Institut de Recherches Cliniques de Montréal (IRCM). RRL holds a scholarship from the Fonds de Recherche en Santé du Québec, and SZ has a doctoral Banting and Best scholarship from the Canadian Institutes of Health Research.
All human studies have been reviewed and approved by the Research Ethics Committee of the CHUM.
Human and animal rights
All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2008.
Informed consent was obtained from all patients for being included in the study.
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