Background/Purpose: High resolution computed tomography (HRCT) of the chest has become an important modality in the evaluation of interstitial lung disease (ILD). A quantitative CT scoring method using a computer aided diagnostic system to measure the nature and extent of parenchymal diseases has been used to measure treatment response in the scleroderma lung study II (SLSII). The current study aims to describe quantitative CT scores in myositis and antisynthetase syndrome related ILD in comparison to scleroderma ILD (SSc-ILD).

Methods: Quantitative CT scores were performed on HRCT scans obtained from the Abatacept for the Treatment of Myositis-Associated ILD (Attack My-ILD) clinical trial which was a 12-month study including 20 adult patients with antisynthetase syndrome and active ILD (ASSD-ILD). We compared baseline scores with a subgroup of an observational cohort of myositis patients with ILD (Myositis-ILD), and the SLS II cohort which included patients with limited or diffuse scleroderma and active ILD (SSc-ILD). Quantitative CT scores were compared between the 3 ILD cohorts at baseline, and scores over time were compared between the two clinical trial cohorts (ASSD-ILD and SSc-ILD). Images were also assessed visually by thoracic radiologists.

Results: Baseline characteristics are described in Table 1. The ASSD-ILD group had lowest forced vital capacity(FVC) and diffusing capacity (DLCO) and highest quantitative scores for ground glass (QGG), fibrosis (QLF) , honeycombing (QHC) and total sum of disease (QILD) among the 3 cohorts. Zone of maximum involvement was shared throughout upper, middle and lower zones in ASSD- and Myositis-ILD, unlike SSc-ILD where 94% had maximum disease in the lower zones of the lung. Visual review of the ASSD-ILD and Myositis-ILD images revealed a pattern distinct from SSc-ILD (Figure 1). In ASSD- and Myositis-ILD, there are areas of confluent fibrosis that mimic organizing pneumonia with fibrosis and volume loss. Also, the disease extends to the periphery of the lung, unlike SSc-ILD which tends to spare the periphery. Both diseases demonstrate ground glass opacity and reticulations with bronchiectasis. In comparing subjects that showed favorable treatment response from the two clinical trials, the ASSD-ILD patient showed marked improvement in CT images (Figure 1-A to C) which was also reflected in changes in their quantitative scores (Figure 1-B to D), whereas in the SSc-ILD subject the improvement was more subtle (Figure 1 E,F to G,H). Mean changes in lung physiology and quantitative CT scores over the trial period demonstrated that QLF scores in the ASSD-ILD cohort showed greater improvement compared to the SSc-ILD cohort despite its shorter follow up time and the lack of differences in changes in FVC or DLCO between the groups (Table 2).

Conclusion: HRCT images from ASSD-ILD and Myositis-ILD demonstrate a pattern that is distinct from SSc-ILD. ASSD-ILD shows more marked improvement in HRCT images with treatment than SSc-ILD which is reflected as a significantly greater decrease in quantitative CT scores over time compared to SSc-ILD. Further studies are needed to better characterize and quantify HRCT images in myositis and antisynthetase syndrome related ILD.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/quantitative-scoring-of-high-resolution-chest-computed-tomography-hrct-images-in-myositis-and-antisynthetase-syndrome-related-interstitial-lung-disease-in-comparison-to-scleroderma-related-interstit/