(344) Implementation of a Tiered System of Screening for Cystic Fibrosis Related Diabetes Using Oral Glucose Tolerance Testing and Continuous Glucose Monitoring

Background: Cystic fibrosis related diabetes (CFRD) is an impactful complication occurring in 5% of children and 31% of adults with CF [1}. A diagnosis of CFRD is often preceded by decline in lung function [2] making screening a crucial aspect of preventative care. Current guidelines [3] recommend an annual oral glucose tolerance test (OGTT) for all patients with CF over 9 years of age. This can have diagnostic limitations for mild impairments in glucose tolerance (IGT) and miss transient hyperglycemia diagnostic of CFRD. Furthermore, endocrine consultation is a highly sought resource but is best utilized when informed by data beyond a single abnormal OGTT. Continuous glucose monitoring (CGM) can provide useful adjunctive data to an abnormal OGTT and direct the urgency of referrals to endocrinology, while supporting early intervention for CFRD. The aims of this initiative were to 1) increase the percentage of patients screened using targeted education on the benefits of CFRD screening and early diagnosis, and 2) develop a two-tiered system for screening using OGTT and CGM to stratify patient risk and need for endocrinology evaluation at a single CF Center.

Methods: A CFRD screening protocol informed by CFRD Consensus Guidelines was developed in collaboration with Endocrinology and included second tier screening using CGM for all patients with abnormal OGTT results. Patients eligible for screening were identified during team pre-visit planning. Education was provided on the value of CFRD screening, the potential spectrum of results and follow up. A 10-day period of CGM was recommended for any patient with an abnormal OGTT. Follow up of abnormal testing was determined based on collaborative review of data by CF and endocrine providers. Measures included % of eligible patients screened yearly, % of patients with abnormal OGTT results, and % of patients with abnormal results who had second tier screening with CGM.

Results: Ninety- two patients with CF > 9 years receive care at this CF Center. Of these 9% have an established diagnosis of T1DM or CFRD leaving 84 patients eligible for screening. Based on past data, it is anticipated CFRD would be identified in 5% of patients and IGT in 20% of patients screened using traditional OGTT alone. To date 31% have had OGTT screening. Of those screened 30% had results meeting diagnostic criteria for IGT or CFRD and 10% have had second tier screening using CGM. Results from a year of two-tiered screening will be completed and presented.

Conclusions: Current screening methods for CFRD can be inadequate in identifying IGT or transient hyperglycemia. Implementation of a second tier of screening using CGM data can inform the need for additional evaluation and/or intervention. Close collaboration between the CF and endocrinology teams supports earlier identification of patients at highest risk for health decline related to a diagnosis of CFRD.

Acknowledgements: This work was supported by a Prince Scholar Grant from Lurie Children's Hospital.
Dexcom CGM starter kits were provided by Dexcom, Inc.

References: [1] CFF Patient Registry Highlights (2019) Cystic Fibrosis Foundation.
[2] Thompson, EF, Watson, D. Benoit, CM et al. (2020) The association of pediatric CFRD screening on clinical outcomes. J of Cystic Fibrosis 19(2).
[3] Moran A, Brunzell C, Cohen RC, et al. Clinical care guidelines for CFRD: a position statement of the American Diabetes Association and a clinical practice guideline of the CFF, endorsed by the Pediatric Endocrine Society. Diabetes Care. 2010;33(12):2697-708.