Correlation analysis between quantitative lung ultrasound parameters and pulmonary function in idiopathic pulmonary fibrosis: an observational study.

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal interstitial lung disease (ILD) with limited monitoring tools. Lung ultrasound (LUS) has emerged as a promising radiation-free alternative, but its clinical utility in IPF requires further validation. This study aimed to comprehensively evaluate the correlation between quantitative LUS parameters and established disease severity markers in IPF patients.

METHODS

An observational study was conducted in eligible IPF patients. Participants underwent comprehensive assessment including clinical questionnaires, pulmonary function tests, serum KL-6 measurement, high-resolution computed tomography (HRCT), and a standardized LUS protocol. Correlation and multiple linear regression analyses were performed to examine the relationships between LUS indices and conventional severity markers.

RESULTS

The analysis included 47 IPF patients stratified by DLCO% predicted (≥60% mild, <60% moderate-severe). The moderate-severe group showed significantly higher B-line counts, B-line scores, pleural scores, diaphragm thickness and lower diaphragm thickening fraction (p < 0.05). B-line count, B-line score, pleural score, and diaphragmatic thickness all exhibited significant negative correlations with DLCO% predicted (r = -0.84, p < 0.01; r = -0.87, p < 0.01; r = -0.80, p < 0.01; and r = -0.58, p < 0.05, respectively). Conversely, the diaphragmatic thickening fraction showed a significant positive correlation with DLCO% predicted (r = 0.44, p < 0.05). Multivariable regression analyses identified DLCO% predicted as a significant negative indicator of B-line count (β = -0.604, p < 0.001), B-line score (β = -0.846, p < 0.001), and pleural score (β = -0.860, p < 0.001). SGRQ score was positively associated with both B-line count (β = 0.308, p = 0.019) and B-line score (β = 0.336, p = 0.012). Warrick score exhibited a positive association with B-line count (β = 0.240, p = 0.015) but a negative association with pleural score (β = -0.295, p = 0.011). BMI also showed a negative association with pleural score (β = -0.233, p = 0.016).

CONCLUSION

Quantitative LUS parameters show strong and consistent correlations with clinical, functional, serological, and radiographic markers of IPF severity. These findings support the potential utility of LUS as a comprehensive, non-invasive tool for multidimensional disease assessment in IPF patients.