Ways to predict interstitial lung disease in patients with systemic sclerosis: results of an observational study

In patients with systemic sclerosis (SSc), interstitial lung disease (ILD) is a factor in the decline of functional capacity up to disability and is also the leading cause of death. Therefore, one of the most important tasks in the treatment of this group of patients is not only to detect involvement of respiratory system, but also to predict the likelihood of its development.

Objective: to study the possibility of predicting the development of ILD and advanced ILD in patients with SSc.

Material and methods. The study included 79 patients with SSc (mean age 64.4±11.5 years; 94.9% women) from the Registry of myositis, SSc and Mixed Connective Tissue Diseases (РЕМИССиС) who underwent high-resolution computed tomography (HRCT) of the lungs. Classification trees (CTr) were constructed to predict the development of widespread ILD using the CHAID algorithm (exhaustive). All patients were tested for antibodies against Scl-70 (anti-Scl-70), CENP-B (anti-CENP-B), and PmScl (anti-PmScl).

Results and discussion. ILD signs according to HRCT were detected in 53 patients. Fibrotic (34.2%) and cellular (15.2%) types of nonspecific interstitial pneumonia were the most common, and common interstitial pneumonia was less frequent (11.4%).The presence of ILD and advanced ILD (involvement of more than 20% of the lung parenchyma) were significantly associated with the detection of any autoantibodies, except anti-centromere antibodies, an increase in pulmonary artery systolic pressure, a decrease in forced vital capacity, diffusing capacity of the lungs, blood oxygen saturation at rest, and all parameters of six-minute walk test (6MWT), and complaints of shortness of breath. In addition, the presence of extensive ILD was also significantly associated with diffuse SSc and with SSc without skin manifestations.

In establishing the CTr, it was found that the development of widespread ILD was unlikely in individuals who were able to walk more than 440 m in 6MWT and had neither anti-Scl-70 nor anti-PmScl.

Significant associations were also found between the radiological pattern of ILD and the types of disease-specific antibodies.

Conclusion. The 6MWT data in conjunction with the results of testing for SSc-specific autoantibodies provide a very accurate prediction of the presence and extent of ILD. It is advisable to include these indicators in the algorithm for screening and monitoring patients with SSc.

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