Interstitial lung disease (ILD) is a frequent extra-articular manifestation of RA associated with increased mortality. High-resolution CT (HRCT) is used for diagnosis and follow-up, but its accuracy is counterbalanced by high costs and radiological risk. In the presence of ILD, lung US (LUS) detects vertical artefacts called B-lines. The aims of the present study were to evaluate the accuracy of LUS in the diagnosis of ILD in RA and to validate the use of a pocket-size US device (PS-USD) as a screening tool.
LUS was performed with standard equipment by a trained physician through longitudinal scans following anatomical lines: 72 segments were considered (28 anteriorly and 44 posteriorly) and B-lines were counted in each segment. A B-lines score >10 identified a positive examination (presence of ILD). A second LUS session for positive/negative judgment was performed by a short-trained physician using a PS-USD.
Thirty-nine patients were studied. The sensitivity and specificity of standard LUS vs HRCT were 92% and 56%, respectively. The B-line score was significantly correlated with HRCT score (r = 0.806). A total of 29 patients were studied with a PS-USD. Sensitivity and specificity for PS-USD vs HRCT were 89% and 50%.
The sensitivity of LUS in the detection of ILD supports its use as a screening test for ILD in RA patients, even in the ambulatory setting with a PS-USD. The strong correlation between echographic and HRCT scores indicates LUS is a valid tool for grading and follow-up of ILD.