Assessing Reliability, Reproducibility, and Adherence of Home Spirometry in Patients With Idiopathic Pulmonary Fibrosis: A Korean Multicenter Prospective Study

초록

Rationale: Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease that requires regular lung function monitoring to assess disease progression. Forced vital capacity (FVC) is a main indicator of IPF progression, typically measured through on-site spirometry. However, frequent hospital visits may be burdensome for patients, and home spirometry can offer a potential alternative for continuous lung function monitoring. Although home spirometry has shown promise in chronic respiratory disease, data on its use among Korean patients with IPF are limited. We aimed to evaluate the reliability, reproducibility, and adherence of home spirometry compared to on-site measurements in a Korean IPF cohort.Methods: This multicenter prospective observational study enrolled 120 IPF patients from 12 medical institutes across South Korea. Participants performed home spirometry (SPROLENIS, JNBIO, South Korea) 10 times over five days at 12-hour intervals (8:00 AM and 8:00 PM) in each season for one year, following standardized training to ensure consistent device use. On-site spirometry was used as the reference. Reliability and agreement between home and on-site spirometry were assessed using intraclass correlation coefficients (ICCs) and Bland-Altman analysis. Reproducibility of home spirometry was evaluated using the standard deviation (SD) and coefficient of variation (CV, calculated as SD/mean × 100) for FVC values, while adherence was categorized as good (≥8 tests), fair (5-7 tests), or poor (≤4 tests).Results: Among all patients, the mean age was 68.4 years, with 85.0% being male and 77.5% having a history of smoking. Participants completed an average of 8.1 home spirometry tests each, with home FVC values showing a strong correlation with on-site FVC measurements (FVC % predicted: r = 0.834; FVC, L: r = 0.926; both p < 0.001) (Figure). Reliability analysis using the intraclass correlation coefficient (ICC) indicated excellent agreement between home and on-site FVC% predicted (ICC = 0.909; 95% CI: 0.889-0.937), supporting the robustness of home spirometry data. Bland-Altman analysis showed a mean difference of -8.2% in FVC % predicted, with 95% limits of agreement ranging from -22.9% to 6.5% predicted, suggesting satisfactory concordance. The mean SD for home FVC % predicted was 3.8%, with a CV of 6.4 ± 9.3%, demonstrating acceptable reproducibility. Adherence was high, with 70.8% of participants classified as good users (≥8 tests), 20.0% as fair users, and only 17.5% as poor users.Conclusions: Home spirometry could be a reliable and reproducible option for monitoring lung function in patients with IPF, potentially serving as an alternative to on-site measurements.