Background/Purpose: Lung ultrasound (LUS) is a non-invasive imaging tool to evaluate distribution and severity of interstitial lung disease (ILD). Utility of LUS has been examined mainly in patients with systemic sclerosis (SSc), and B-line scores assessed by LUS were shown to correlate with semiquantitative scores of chest high-resolution computed tomography (HRCT). However, little is known about performance of LUS in ILD associated with idiopathic inflammatory myopathy (IIM) or anti-synthetase syndrome (ASS). The aim of this study was to investigate utility of LUS in patients with IIM/ASS, by focusing on correlations of B-line score with morphological features on HRCT.

Methods: A total of 64 patients, including 30 with SSc-ILD and 34 with IIM/ASS-ILD were selected from a prospective LUS registry of Nippon Medical School Hospital based on fulfillment of one of classification criteria for SSc, IIM, or ASS and availability of chest HRCT and LUS images performed simultaneously. The degree of B-line was semiquantitatively scored using a 4-8 MHz microconvex transducer, and a sum of the B-line at 14 scan sites was used as a total B-line score. ILD images on HRCT were scored according to the method proposed by the Scleroderma Lung Study (SLS) by two investigators in a blinded fashion. The scores assessed included pure ground-glass opacity (pGGO), fibrosis, honeycombing, and consolidation, and the sum of pGGO, fibrosis, and honeycombing scores was regarded as total SLS score. In some analyses, the original SLS score was modified to include the consolidation score. Single regression analysis was used to evaluate correlations of total B-lines with SLS scores of individual morphologies and the total score. Multiple regression analysis was carried out to identify independent morphological features of HRCT contributing to total B-lines.

Results: Total B-line score correlated with total SLS score in patients with SSc-ILD (r = 0.79, P < 0.001), but the correlation was much weaker in patients with IIM/ASS-ILD (r = 0.46, P = 0.006) (Figure 1). When correlations of total B-line score with individual morphological patterns on HRCT were examined, total B-line score was significantly correlated with fibrosis (r = 0.76, P < 0.001) and weekly with honeycombing (r = 0.44, P = 0.015) and consolidation (r = 0.38, P = 0.040) in patients with SSc-ILD. On the other hand, in patients with IIM/ASS-ILD, total B-line score was correlated with pGGO (r = 0.48, P = 0.005) and consolidation (r = 0.57, P < 0.001) (Figure 2). Multiple regression analysis revealed contribution of different morphological patterns on HRCT to total B-line score: fibrosis (β = 0.743, P < 0.001) and honeycombing (β = 0.326, P = 0.007) in SSc-ILD, while consolidation (β = 0.497, P = 0.006) and fibrosis (β = 0.320, P = 0.040) in IIM/ASS-ILD. Finally, inclusion of the consolidation score in the original total SLS score resulted in improvement of correlation with total B-line score in patients with IIM/ASS-ILD (r = 0.67, P < 0.001) (Figure 1).

Conclusion: B-lines detected by LUS reflect different HRCT morphological features in patients with SSc and IIM/ASS. This difference should be considered upon interpreting total B-lines upon evaluation of ILD in clinical practice.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/b-line-of-lung-ultrasound-reflects-different-morphological-features-on-chest-hrct-between-interstitial-lung-disease-associated-with-systemic-sclerosis-and-myositis/