Symposium Summaries

Since the advent of glucose monitoring, our ability to monitor blood glucose levels in real time has become increasingly sophisticated and accurate. Determining one’s blood glucose accurately is key to making a diagnosis of diabetes and for optimal glucose control. Technological advances now allow us the ability to monitor continuous glucose patterns in real time and retrospectively. While most continuous glucose monitoring (CGM) research to date has been in individuals with type 1 and type 2 diabetes, its applications in cystic fibrosis-related diabetes (CFRD) are increasing. This symposium will review the CGM literature with a focus on CF and discuss a practical approach to use of CGM in the care of patients with CFRD. CGM and Screening for CFRD: CGM has been validated in individuals with CF (1) and has been employed for well over a decade in the study of early glucose abnormalities in this population (2,3). Unique to CF is the high rate of diabetes which develops in up to 20-30% of adolescents and 30-50% of young adults (4). CFRD is associated with decline in pulmonary function, weight loss, and increased mortality (5-7). Because classic symptoms of diabetes such as polyuria and polydipsia are typically absent at CFRD onset, efforts have increasingly turned towards early detection and treatment of the disease. CGM detects early glucose abnormalities before traditional diabetes screening tests and offers a more complete picture of free-living glucose patterns compared to simpler metrics such as the hemoglobin A1c (HbA1c) or oral glucose tolerance test (OGTT). CGM therefore may be the optimal tool for detecting early dysglycemia in this population. What is the evidence? CGM abnormalities have been found to correlate with pulmonary function decline (8,9), weight loss (10), as well as increased rates of P. aeruginosa (9) in patients with CF. CGM abnormalities have also been found to be predictors of worsening glucose tolerance and CFRD on OGTT (11,12). Studies are now demonstrating links between specific CGM abnormalities and impairments in insulin secretion (13,14). However, larger prospective studies are still needed to confirm the clinical relevance of these CGM abnormalities and to determine what CGM thresholds warrant treatment to prevent nutritional and pulmonary function decline. Historically, reporting of CGM measures has not been standardized which has made comparison and pooling of data from different studies challenging. Consensus guidelines are now available with recommendations advocating a systematic approach to reporting of CGM data (15,16). However, how we interpret these data in the context of CFRD outcomes requires ongoing study. CGM and the Management of CFRD: The current standard for day-to-day glucose monitoring in CFRD is with fingersticks or self-monitoring of blood glucoses (SMBG). However, this is burdensome and difficult for many patients to consistently adhere to. In non-CFRD populations, a number of studies have now shown that consistent use of CGM reduces hyperglycemia and hypoglycemia, increases time in range, and increases quality of life in both children and adults with diabetes (17-20). Studies on the use of real-time CGM for glucose management in CFRD are scarce (21) and uptake of diabetes technology in the CF population tends to be low (22). Studies on use of CGM for CFRD management are needed to better understand the barriers to technology uptake and define the populations who will benefit most from CGM. Future directions: Advancements in diabetes technology are bringing about devices with increased accuracy, comfort, and increased automation of insulin delivery. Patients with CFRD stand to benefit immensely as the landscape of diabetes management continues to evolve. Further research should take into account unique aspects of CFRD pathophysiology and an understanding of the complexities related to treatment burden and decision making in this population. References: 1. O’Riordan SM, et al. Validation of continuous glucose monitoring in children and adolescents with cystic fibrosis: a prospective cohort study. Diabetes Care. 2009;32(6):1020-2. 2. Dobson L, et al. Conventional measures underestimate glycaemia in cystic fibrosis patients. Diabet Med. 2004;21(7):691-6. 3. Franzese A, et al. Continuous glucose monitoring system in the screening of early glucose derangements in children and adolescents with cystic fibrosis. J Pediatr Endocrinol Metab. 2008;21(2):109-16. 4. Moran A, et al. Cystic fibrosis-related diabetes: current trends in prevalence, incidence, and mortality. Diabetes Care. 2009;32(9):1626-31.