Correlation Between Lung Clearance Index (LCI) and Forced Expiratory Volume (FEV1) in Children with Cystic Fibrosis (CF): A Cross-Sectional Study

Background: The Lung Clearance Index (LCI) serves as a non-uniform ventilation index utilized for monitoring pulmonary function in patients with cystic fibrosis (CF). Lung Clearance Index exhibits higher sensitivity compared to forced expiratory volume in 1 second (FEV1) for early detection of lung disease and does not necessitate active patient cooperation, as required for FEV1 measured through spirometry. Presently, FEV1 is the standard parameter employed for monitoring lung function in CF patients. Objectives: The objective of this study was to assess the correlation between LCI and FEV1 in patients with cystic fibrosis. Methods: This cross-sectional study enrolled children aged 6 to 18 years with confirmed CF diagnosis, who were referred to the CF clinic at Children's Medical Center Hospital (Tehran, Iran). Participants completed consent forms and subsequently underwent pulmonary function tests. Lung Clearance Index was calculated using the exhaling-D device via the Multiple Breath Washout (MBW) method, followed by FEV1 assessment through spirometry. Results: The study included 52 patients with an average age of 12 years, among whom 52% were males. The mean ± standard deviation of FEV1 and LCI were 80.2% ± 25.3 and 8.9 ± 2.8, respectively. A significant inverse relationship was observed between these two parameters in the study (r = -0.49, P = 0.001). Conclusions: These findings further underscore the potential utility of LCI, which offers ease of administration and demonstrates high reliability and accuracy compared to FEV1 for monitoring pulmonary function in CF patients.