Surfactant proteins-A and D as important serum markers for interstitial lung disease in patients with polymyositis or dermatomyositis

Abstract

To explore the possible diagnostic values of serum surfactant protein-A (SP-A) and surfactant protein-D (SP-D) for interstitial lung diseases (ILD) in patients with polymyositis or dermatomyositis (PM/DM). Serum MCP-1 concentrations were measured by enzyme-linked immunosorbent assay (ELISA) in 100 adult PM/DM patients, 20 patients with pulmonary infection and 42 healthy controls. And the association with their clinical features and serum levels of SP-A and SP-D was analyzed. The serum levels of SP-A and SP-D in the PM/DM patients with ILD were both significantly higher than those without ILD and healthy controls (all P < 0.01) while there were no significance differences with those with infectious lung diseases (P > 0.05). The sensitivity of serum abnormal levels of SP-A, SP-D and combination of SP-A and SP-D for ILD in PM/DM patients were 66.1%, 64.3% and 80.0% and the specificity 72.7%, 72.7% and 70.2% respectively. The serum levels of SP-A were positively correlated with serum ferritin and C-reactive protein (CRP) and negatively with percent carbon monoxide diffusing capacity (DLCO%) (r = -0.474, P < 0.05), VC% (r = -0.404, P < 0.05) while the serum levels of SP-D were negatively correlated with circulating CD3+T cells (r = -0.244, P < 0.05) and CD4+T cells (r = -0.277, P < 0.05) in PM/DM patients. Furthermore, SP-A was an independent risk factor for death of ILD in PM/DM (OR 1.032, 95%CI 1.006 - 1.059, P < 0.05). SP-A and SP-D may be potential useful serum markers for the diagnosis of ILD in PM/DM patients. And the combined detection of SP-A and SP-D offers a higher sensitivity than either marker alone. As a risk factor, serum SP-A can predict the prognosis of PM/DM patients with ILD.