Continuous Glucose Monitoring As A Useful Decision-Making Tool For Adults With Cystic Fibrosis

摘要

To the Editor: In cystic fibrosis (CF) there are established links between poor glycemic control and poor respiratory function (1), as well as a decline in body mass index (BMI) (2). Development of CF-related diabetes (CFRD) increases with age and thus is becoming more frequent in adult clinics with increased longevity and the additional pancreatic stress with high dose glucocorticoid following successful lung transplant (3). Glycated hemoglobin (HbA1c) is not a reliable measure of diabetic status in CF, and oral glucose tolerance test (OGTT) may both over and underestimate daily hyperglycemia (4). We report the results of a clinic-based pilot study which aimed to determine if use of continuous glucose monitoring (CGM) (4) in adults with CF is tolerable and helpful to patients, useful to clinical practice decision-making and if it improves clinical status. No other studies have been conducted using CGM in adults with CF with the express purpose of improving clinical decision-making and clinical status, but this is the evidence that would assist services in allocating resources for this technology. Patients were recruited between August and December 2011 from the CF Clinic at Royal Prince Alfred Hospital, Sydney, Australia. This clinic has 240 patients, of whom 25% have CFRD. The inclusion criterion was the immediate requirement of a management decision that might be enhanced by the additional glucose metabolic information provided by CGM as determined by the clinic endocrinologists (LS & KS). Exclusion criteria were a current acute exacerbation of respiratory disease and significant coagulopathy with CF-related liver disease. Approval for the study was obtained from the Hospital’s Ethics Committee (X11-0106 & HREC/11/RPAH/146). Informed consent was obtained before enrolment to the study. The participants undertook CGM (iPro2?; Medtronic MiniMed, Northridge, CA, USA) for six days while continuing their normal diet, lifestyle and treatments. Fingerstick capillary blood glucose levels, before meals and bedtime, were used to retrospectively calibrate the monitors. After the CGM period, participants completed a qualitative questionnaire to assess their experience with the device. Using CGM output provided by CareLink? Pro software (Medtronic MiniMed, Northridge, CA, USA) and standard clinical information, a management decision was made incorporating published clinical guidelines and patient input (5). At baseline an OGTT was conducted. At baseline and six months follow up, participants had a clinical examination including respiratory function (FEV1), HbA1c, and BMI assessment. Descriptive statistics were performed to examine clinical data at baseline and 6 months follow up. Pearson’s correlation coefficient was used to determine associations between variables.Fourteen participants (11 females; median age 25 years [range 21–58]) enrolled in the study and all successfully undertook CGM for the prescribed period. The Table reports individual participant clinical data (and group means) at baseline and follow up along with CGM informed therapy decisions/changes. Four participants (ID# 2, 9, 11 and 14) were excluded from longitudinal analyses with reasons provided in the Table. In the 10 valid cases at follow up, 7 participants had a reduction in HbA1c (mean change -0.8% (95% Confidence Interval: -1.7 to 0.1), 6 participants had a reduction in BMI (mean change 0.0kg/m2, 95% CI: -0.8 to 0.7) and 8 participants had a reduction in FEV1 (L) (mean change -0.12 L, 95% CI: -0.24 to 0.0) and its %-predicted value (mean change -4.7, 95% CI: -9.7 to 0.3). Interpretation of these pilot study results is limited by the small sample size, pre-post design and lack of CGM at follow up.