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%.