Relationship between lung volume and quality of life in patients with interstitial lung disease

This study examined the association between lung volume and QOL determined based on CT and calculated the cut-off lung volume that reflects a decline in the QOL.

This study examined the association between lung volume and QOL determined based on CT and calculated the cut-off lung volume that reflects a decline in the QOL.

Forty-three patients with ILD who visited our Pulmonary Medicine Department between 2017 and 2019 and were followed up for 2 years were included in this study. Theparticipant mean age was 75.5 (SD, 7.7) years, and the Gender-Age-Physiology stage was II (IQR,Ⅰto Ⅱ). Twenty-one and 22 patients had idiopathic pulmonary fibrosis and non-idiopathic pulmonary fibrosis, respectively. As the primary evaluation, lung volumes were assessed using Ziostation2 (Ziosoft, Inc., Tokyo, Japan), a software program for CT image analysis, to calculate the volume of the bilateral whole-lung fields. For QOL assessment, the Chronic Obstructive Pulmonary Disease Assessment Test (CAT), which has been used in previous studies as a simple QOL assessment tool for patients with ILD, was used.Secondary assessments included PFT and biochemical, blood gas, and 6-minute walk tests.

For statistical analysis, Pearson's product-rate correlation coefficient was used to confirm the association between lung volume and 6MWD at diagnosis. Receiver operating characteristic (ROC) analysis was used to calculate the cut-off lung volume that indicated a QOL decline, with a CAT score of ≥10 indicating a decline and a score of 10 indicating maintenance.

A significant relationship was observed between the lung volume and QOL (r = 0.45, p 0.05). ROC analysis showed that the change in lung volume over 2 years was 374 ml (sensitivity, 78%; specificity, 51%; area under the curve, 0.81; p 0.01), indicating a decrease in QOL.

Lung volumes calculated based on CT images in patients with ILD were associated with QOL. The cut-off lung volume indicating a decreased QOL was 374 ml.

By calculating the cut-off lung volume that reflects QOL decline in patients with ILD, it may be possible to determine the presence or absence of QOL decline, even in patients with ILD for whom respiratory function tests cannot be performed.