Lung ultrasound in UIP and NSIP: clinical and functional associations

This study evaluated lung ultrasound (LUS) for distinguishing nonspecific interstitial pneumonia (NSIP) from usual interstitial pneumonia (UIP) and its association with clinical and functional parameters. Seventy-six patients with HRCT-diagnosed UIP ( n = 42) or NSIP ( n = 34) underwent LUS. We analyzed clinical characteristic and LUS parameters, including coalescent (c-LUSS), quantitative (q-LUSS), and pleural scores. Logistic and linear regressions identified LUS parameters associated with UIP/NSIP and pulmonary function tests. ROC analysis evaluated the diagnostic performance of sex combined with pleural line total score. Patients with UIP had higher pleural line total, morphology, disruption, and fragmentation scores (all P < 0.05). Adjusted models identified several independent predictors distinguishing NSIP from UIP, notably the c-LUSS plus pleural line total score (OR: 1.06; 95% CI: 1.01–1.12), q-LUSS plus pleural line total score (OR: 1.07; 95% CI: 1.02–1.13), and pleural line total score (OR: 1.12; 95% CI: 1.03–1.22), alongside specific morphological subscores. The c-LUSS plus pleural line total score (OR: 1.12, 95% CI: 1.02–1.23), q-LUSS plus pleural line total score (OR: 1.1, 95% CI: 1.01–1.2), pleural line total score (OR: 1.14, 95% CI: 1–1.29), pleural thickness score (OR: 1.37, 95% CI: 1.02–1.85) remained independently associated with the severe FEV1. Meanwhile, the q-LUSS (β: −5.88; 95% CI: −11.33 to − 0.44) and B-line score of 3 or more (β: −7.01; 95% CI: −13.48 to − 0.54) were independently associated with 6MWD in UIP/NSIP patients. Whereas, these LUS indicators cannot reliably predict the severity of diffusion dysfunction indexed by DLCO % predicted (all P > 0.05). Combining sex and pleural line total score yielded an AUC of 0.782 (95% CI: 0.677–0.887, bootstrap C-index: 0.772). LUS, especially pleural assessment, may support differentiation between UIP and NSIP, but it cannot replace HRCT or multidisciplinary assessment. It exhibits relatively low performance in evaluating the severity of pulmonary diffusion dysfunction. Further external validation is still needed.