Methods:
This is a single center retrospective analysis of all patients who were admitted to the Hospital for Sick Children for treatment of CF PEx between January 2009 and December 2019, who had acceptable pulmonary function testing with BD response assessed on day 7 ± 3 days of admission. Multiple events for patients with BD testing during different admissions were included in the analysis. This study was approved by the Hospital for Sick Children Research Ethics Board (REB # 1000063663).
Patients were identified using the Toronto CF data base (REB # 1000004851). Baseline characteristics (age, gender, ethnicity, CFTR mutation, BMI, use of inhaled steroids) as well as pulmonary function test results and airway microbiology results were obtained; additionally, clinical charts were reviewed to detect any changes in management that were based on the results of BD response testing.
Spirometry testing was performed by certified and experienced technicians using VMax TM Encore systems - Carefusion, Yorba Linda, CA, USA. All results were acceptable and reproducible meeting ATS/ ERS criteria15. Results were transformed to percent predicted values using the global lung initiative (GLI) equations16. Patients were asked to refrain from any use of inhaled short acting beta agonists (SABA) for at least 4 hours and inhaled long acting beta agonists (LABA) for at least 12 hours prior to BD response testing. Spirometry and BD response testing was performed in accordance with published ATS/ERS guidelines15.
All statistical analyses were performed in Stata 16.1 (StataCorp, College Station, TX). Quantitative data were expressed as median and interquartile range (IQR), whereas qualitative data were shown as frequencies and percentages. Correlations between outcomes were assessed using Pearson correlation coefficients. Comparison of categorical variables were calculated using Fisher’s exact test and Mann-Whitney test was used for nonparametric variables. All statistical tests were two-tailed, and the significance level was 95%.