Background: Soluble mannose receptor, sCD206, is a marker of alternatively activated macrophages. Activated macrophages play important roles in connective tissue disease (CTD) and lung fibrosis. Interstitial lung disease (ILD) is a common complication of CTD, which leads to poor prognosis, especially in a pattern with usual interstitial pneumonia (UIP). Similarly, idiopathic pulmonary fibrosis (IPF) is also characterized by UIP. Compared with IPF, the prognosis of CTD-associated UIP is tightly correlated with early treatment. In the present study, we aimed to evaluate the clinical significance of sCD206 in discriminating CTD-associated UIP from IPF.
Methods: The serum level of sCD206 was determined in 48 patients with CTD-associated UIP, 54 IPF patients and 27 healthy controls. The clinical significance of sCD206 was also evaluated.
Result: Patients with CTD-associated UIP had a higher level of sCD206 compared with healthy controls and IPF patients (p<0.001, p<0.001, respectively). A cutoff value of sCD206 at 523.8 ng/mL could be a useful marker for distinguishing CTD-associated UIP from IPF. Moreover, 15 decedents with CTD-associated UIP exhibited a greater level of sCD206 compared with 33 survivors (p=0.030), and the elevated sCD206 level was associated with a higher mortality rate (log-rank test, p=0.003). Age and gender-adjusted multivariate Cox regression analysis showed that sCD206 (>444.2 ng/mL) was an independent predictor of survival (p= 0.026).
Conclusions: Collectively, the serum level of sCD206 could be a useful marker for distinguishing CTD-associated UIP from IPF and associated with a poor survival of CTD-associated UIP.