The anti-melanoma differentiation-associated gene 5 (anti-MDA5) antibody was significantly associated with dermatomyositis associated with interstitial lung disease (DM-ILD) and poor survival in patients. However, there was no convenient and accurate biomarker can predict the poor prognosis of anti-MDA5 positive DM-ILD. This study aimed to evaluate the clinical significance of osteopontin (OPN) in anti-MDA5 positive DM-ILD patients.
The subjects were 43 patients diagnosed DM-ILD with anti-MDA5 antibody. The clinical data were obtained through a review of patient medical records. The serum samples were collected at the time of initial admission and detected for OPN concentrations and ferritin. In addition, immunohistochemistry analysis for OPN was performed on the lung sections of two patients with DM-ILD and six patients with early-stage lung cancer as normal control.
The median value of serum OPN in patients with anti-MDA5 positive DM-ILD was 1755.65 pg/ml. Immunohistochemical findings for OPN suggested that the expression of OPN in alveolar epithelial cells and macrophages of anti-MDA5-positive ILD patients was more obvious. Significant correlations between serum OPN and ferritin levels were observed (r = 0.317, P = 0.038). Although OPN and ferritin were both associated with mortality in Univariate Cox hazards analysis, OPN was an independent predictor of the prognosis of DM-ILD rather than ferritin in Multivariate Cox hazards analysis.
OPN can be expressed in lung tissues but also can exist as a secreted form in serum, and serum OPN may be a more valuable prognostic biomarker in DM-ILD patients with anti-MDA5 antibody than the serum ferritin.

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