Lung ultrasound outperforms symptom-based screening to detect interstitial lung disease associated with rheumatoid arthritis.

Objectives: Interstitial lung disease associated with rheumatoid arthritis (RA-ILD) is linked to high mortality. Currently, effective screening tools are lacking. We assessed the role of symptoms and lung ultrasound (LUS) as potential screening tools.

Methods: 116 adult patients with RA presenting to the rheumatology outpatient clinic underwent high-resolution CT (HRCT) scans, pulmonary function tests, LUS (72 zones) and completed a Visual Analogue Scale (VAS) for cough and modified Medical Research Council dyspnoea scale (mMRC). Kruskal-Wallis (KW) tests evaluated the correlation between clinical-radiological HRCT score (no ILD, non-specific abnormalities, subclinical ILD or ILD) and the B-lines on LUS, diffusion capacity (DLCO%pred), forced vital capacity (FVC%pred), VAS Cough and mMRC. Sensitivity and specificity analyses were performed to assess symptom-based questionnaires and the number of B-lines to detect RA-ILD. Area under the receiver operating characteristics (AUROC) for detecting clinical ILD and subclinical ILD were calculated.

Results: In 11.8% of patients, an ILD was detected on HRCT. Additionally, in 5%, a diagnosis of subclinical interstitial lung changes was made. The number of B-lines was most strongly associated with the clinical-radiological score (KW χ²=41.2, p=<0.001). DLCO%pred was also significantly correlated with the clinical-radiological score (KW χ²=27.4, p=<0.001), but FVC%pred, mMRC and VAS cough were not. Cough and dyspnoea only weakly predicted the ILD score in the sensitivity-specificity analyses, while B-lines showed AUROCs>0.9 for predicting subclinical and clinical ILD.

Conclusion: LUS is a promising tool for early detection of RA-ILD, outperforming symptom-based questionnaires or the presence of dyspnoea or cough.