Simplified ultrasound scoring scale (LUNA score) for the detection of interstitial lung disease using point-of-care lung ultrasound in systemic autoimmune diseases

Abstract

Background and objective

Interstitial lung disease (ILD) is a frequent and severe complication of systemic autoimmune diseases (SADs). Its early diagnosis, based on periodic high-resolution computed tomography (HRCT), involves radiation exposure. Lung ultrasound (LUS) has shown good performance in ILD detection. The aim of this study was to design a new simplified lung ultrasound scoring scale based on the quantification of B-lines and pleural irregularities (LUNA score) for ILD detection using a point-of-care ultrasound device.

Patients and methods

Between November 2020 and December 2021, HRCT and LUS (using a Butterfly iQ® device and a 14-zone scanning protocol) were performed in 88 patients with SADs, 69 of whom met criteria for systemic sclerosis. The LUNA score, which combines B-line counts and pleural irregularities to detect ILD, was constructed using logistic regression. Diagnostic performance was evaluated through ROC analysis, 10-fold cross-validation, and inter-observer reliability.

Results

The LUNA score showed excellent inter-observer agreement (κ = 0.810) and utility for ILD diagnosis, with an area under the curve (AUC) of 0.968 (95% CI: 0.926–1.0). The optimal cut-off point (≥38 points) demonstrated a sensitivity of 97.2% and a specificity of 92.3% (Youden index 0.895). Cross-validation yielded an average AUC of 0.963.

Conclusions

The LUNA score is a simple scale based on objective items that are easily identifiable via LUS. In this study, it demonstrated excellent performance for ILD detection in patients with SADs, supporting its potential incorporation into diagnostic algorithms and the reduction of unnecessary HRCT scans.