(3) Cystic Fibrosis Related Diabetes – Adherence to Screening at a Large Clinical Center

Background: Cystic fibrosis-related diabetes (CFRD) is increasing in incidence among patients with cystic fibrosis as the life expectancy improves with the advent of CFTR modulator treatments. The current Cystic Fibrosis Foundation screening guidelines, last updated in 2010, recommend screening for CFRD with a 2-hour OGTT annually, starting at 10 years of age [1]. Prior studies have demonstrated that centers with higher rates of screening with OGTT’s diagnose CFRD earlier and have slower rates of pulmonary decline [2]. Questions remain as to the best way to screen for diabetes among patients with CF given their complexity. The aim of our study was to describe the adherence rates of ordering OGTT’s and rates of completion of OGTT’s at Michigan Medicine in CF populations.

Methods: The cohort was defined as patients with CF who were eligible for screening with an OGTT between 2010 and 2021. We excluded patients with a diagnosis code of CFRD. We defined screen eligible years as the number of years between 2010 and 2021 in which the CF patients should have been screened with an OGTT. We defined the number of OGTT tests ordered per patient by summing the number of OGTT orders per year that were performed over the period. We defined the number of OGTT tests completed per patient by summing the number of completed OGTT tests for the period. We defined order adherent as having a % ordered per patient that was >/= 75%. We defined test adherent as having a percent performed per patient that was >/= 75%. We analyzed the differences in these measures based on race, gender, and age. We examined the outcomes of screening (pre-diabetes or diabetes) based on OGTT results and HbA1c.

Results: At Michigan Medicine, among all patients eligible for screening with an OGTT, there was a center-level rate of ordering OGTT’s of 16.5%, and a rate of screening with completed OGTT’s of 13.8 %. 83% OGTT’s ordered were completed by patients, while 100% of HbA1c’s ordered were completed. Of the OGTT’s completed, 24% screened positive for pre-diabetes and 3.4% screened positive for diabetes. Of the HbA1c performed, 31% screened positive for pre-diabetes, and 1.2% screened positive for diabetes. There were significant differences by age in rates of screening (p< 0.01) and rates of completion (p< 0.01) with higher rates of screening in younger vs older patients, but not by gender or race (Table 1).

Conclusions: Overall, rates of adherence to OGTT ordering and completion were suboptimal. Patients had a higher rate of adherence to diabetes screening with HbA1c compared to OGTT and ordering adherence was higher for pediatric vs adult patients. While current CFF guidelines recommend the OGTT as the standard of screening for CFRD, OGTT testing is more burdensome, and takes more time to complete among a patient population that already has high healthcare utilization. Continued analysis of our data is needed to further determine outcomes of screening, specifically trends in BMI, pulmonary function tests (FEV-1 and FEF25-75), number of hospitalizations and variations in insulin use.

Acknowledgements:

References: 1. Granados, A., et al., Cystic fibrosis related diabetes: Pathophysiology, screening and diagnosis. J Cyst Fibros, 2019. 18 Suppl 2: p. S3-S9.

2. Franck Thompson, E., et al., The association of pediatric cystic fibrosis-related diabetes screening on clinical outcomes by center: A CF patient registry study. J Cyst Fibros, 2020. 19(2): p. 316-320.