[Surfactant proteins A and D as biomarkers of disease activity in diffuse interstitial pneumonia]

We evaluated the clinical significance of surfactant proteins A (SP-A) and D (SP-D) as useful markers of disease activity in patients with diffuse interstitial pneumonia. Serum concentrations of SP-A and SP-D were measured by the sandwich ELISA method. The serum levels of SP-A and SP-D in patients with diffuse interstitial pneumonia (IIP, CVD-IP, HP, Ra-IP) were significantly higher than the levels in healthy controls, and showed high positive rates. IIP patients characterized by a predominantly ground-glass opacity (GGO) pattern on high-resolution computed tomograms had significantly higher concentrations of serum SP-A. Elevated SP-D levels reflected the extent not only of GGO but also of parenchymal collapse opacity (PCO). It is likely that the mechanisms behind the elevation of SP-A and SP-D do not correlate with pathologic changes in IIP. Serum SP-A and SP-D levels obtained at the time of initial evaluation from 9 patients who died after less than 3 years of follow-up were significantly higher than in patients with survival rates of more than 3 years. Serum SP-A and SP-D may be useful biomarkers of disease activity in patients with IIP.