Continuous glucose monitoring in a cystic fibrosis patient to predict pulmonary exacerbation?

Patients with cystic fibrosis (CF) experience a significant decline in pulmonary status before the diagnosis of cystic fibrosis related diabetes (CFRD). We hypothesized that hyperglycemia may be a factor in the decline of pulmonary function and increased frequency of pulmonary exacerbations. Long term continuous glucose monitoring (CGM) has not been reported in patients with CF and impaired glucose tolerance. We performed CGM for three months in a 17year old male with F508del and F553X CF mutations, baseline forced expiratory volume in 1s (FEV1) of 92% predicted, and impaired glucose tolerance to evaluate changes in glucose levels prior to the diagnosis of a pulmonary exacerbation. Results revealed elevated overnight, fasting and post-prandial glucose levels up to one week prior to diagnosis of a pulmonary exacerbation compared to baseline. In addition, mean glucose was elevated and the patient spent a greater percentage of time with interstitial glucose>140mg/dL up to one week prior to diagnosis of a pulmonary exacerbation. This emphasizes the hypothesis that hyperglycaemia may be a factor in pulmonary exacerbations in this population. This case study strengthens the evidence base to support larger longitudinal studies to understand the impact of glycaemic control and pulmonary function in patients with CF and glucose intolerance.