Utility of Continuous Glucose Monitors for Improved Detection of Cystic Fibrosis-Related Diabetes

Cystic fibrosis-related diabetes (CFRD) can be associated with decline in pulmonary function and nutritional status. Earlier diagnosis of CFRD than offered by annual recommended oral glucose tolerance test (OGTT) and earlier initiation of insulin may help prevent clinical decline. This retrospective study investigates the utility of continuous glucose monitoring (CGM) for detection of hyperglycemia in patients with cystic fibrosis (CF).

In this single-center, retrospective study, we analyzed data from 18 patients with CF over age 10 who had an abnormal OGTT and subsequently had at least 24 h of CGM data. EasyGV software was used to calculate multiple measures of CGM variability. Differences in OGTT and CGM measures were explored across four glucose-tolerance groups: indeterminate, fasting hyperglycemia, impaired glucose tolerance (with or without fasting hyperglycemia), and CFRD.

Multiple CGM measures correlated with components of the OGTT. Across glucose-tolerance groups, significant differences were observed for the OGTT 2-h glucose (p = 0.002), mean of daily differences from CGM (p = 0.03), and standard deviation from CGM (p = 0.02). Approaching significance was the lability index (p = 0.05) from the CGM data. Glucose management indicator (GMI), continuous overlapping net glycemic action (CONGA), glycemic risk assessment in diabetes equation (GRADE), and average daily risk range (ADRR) showed negative correlations with change in forced expiratory volume over 1 s (FEV1) over the year before OGTT.

Markers of glycemic variability may be important variables distinguishing between degrees of abnormal glucose tolerance, including CFRD. This area warrants further research with a larger sample size.