Abstract
Surfactant protein D (SP-D) is considered a serum biomarker of various forms of interstitial lung disease (ILD). In this study, we examined the utility of SP-D as a predictive biomarker for mortality in patients with ILD associated with polymyositis/dermatomyositis (PM/DM) using large-scale multicentre cohort data. We enrolled 381 patients with incident PM/DM-associated ILD in a multicentre retrospective cohort based on the availability of serum SP-D at the baseline. Demographic and clinical characteristics as well as the presence of autoantibodies to melanoma differentiation-associated gene 5 (MDA5) and aminoacyl tRNA synthetase were measured at the time of diagnosis, and follow-up survival data were collected prospectively. Seventy-eight patients died during the median observation period of 18 months, and the majority of patients died of ILD. The SP-D levels at baseline were significantly lower (P = 0.02) in a non-survivor subset than in a survivor subset among the entire enrolled patients. However, the SP-D levels were higher in the non-survivor subset than in the survivor subset based on the stratification by anti-MDA5-positive, anti-ARS-positive and, double-negativity, although there was an only statistically significant difference (P = 0.01) in the double-negative group. Surprisingly, the SP-D levels were within the upper limit of normal, 110 ng/mL, in 54 (87%) of 62 anti-MDA5-positive patients who died. In the double-negative group, the mortality rates were significantly higher (P = 0.002) in a subset with SP-D ≥127.6 ng/mL, the cut-off value for mortality calculated by the receiver operating characteristic curve, than the other subset. All of patients with SP-D <127.6 ng/mL survived. Serum SP-D levels behave differently among patients with stratified by anti-MDA5 antibody, anti-ARS antibody and both negativity in PM/DM-associated ILD. Its use in clinical practice should be applied with caution on the basis of the presence or absence of anti-MDA5 antibody or anti-ARS antibody.
Highlights
Its use in clinical practice should be applied with caution on the basis of the presence or absence of anti-melanoma differentiationassociated gene 5 (MDA5) antibody or anti-aminoacyltRNA synthetase (ARS) antibody
Polymyositis and dermatomyositis (PM/DM) are idiopathic inflammatory myopathies characterized by muscle weakness and skin rash, such as Gottron’s papules or signs and heliotrope rash [1]
A number of circulating biomarkers have been shown to be useful in assessing disease activity and/or predicting the outcomes of interstitial lung disease (ILD) in patients with connective tissue diseases, including PM/DM; these biomarkers include autoantibodies, pneumoproteins, such as Krebs von den Lungen-6 (KL-6) and surfactant protein D (SP-D), and inflammationrelated proteins, such as C-reactive protein (CRP) and a variety of cytokines and chemokines [3]
Summary
Polymyositis and dermatomyositis (PM/DM) are idiopathic inflammatory myopathies characterized by muscle weakness and skin rash, such as Gottron’s papules or signs and heliotrope rash [1]. A number of circulating biomarkers have been shown to be useful in assessing disease activity and/or predicting the outcomes of ILD in patients with connective tissue diseases, including PM/DM; these biomarkers include autoantibodies, pneumoproteins, such as Krebs von den Lungen-6 (KL-6) and surfactant protein D (SP-D), and inflammationrelated proteins, such as C-reactive protein (CRP) and a variety of cytokines and chemokines [3]. Myositis-specific autoantibodies (MSAs) are the most powerful biomarkers for predicting the clinical presentation, response to treatment, and prognosis in patients with PM/DM [4]. It has been shown that the measurement of additional biomarkers potentially enhances the predictive performance of MSAs. For example, in patients positive for anti-melanoma differentiationassociated gene 5 (MDA5) antibody, mortality due to ILD was higher in patients with hyperferritinaemia than in those without hyperferritinaemia [5]. The combined evaluation of multiple biomarkers is used in clinical practice for patients with PM/DM-associated ILD
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