Serum surfactant proteins A and D as prognostic factors in idiopathic pulmonary fibrosis and their relationship to disease extent

Idiopathic pulmonary fibrosis (IPF) is a progressive, life-threatening, int erstitial lung disease of unknown etiology. For optimal therapeutic managem ent of IPF an accurate tool is required for discrimination between reversib le and irreversible types of the disease. However, such noninvasive tools a re few, and even with high-resolution computed tomography (HRCT), which is the most trusted method for doing so, the nature of the disease activity in IPF cannot always be accurately predicted. The aims of the present study w ere to assess the values of surfactant protein (SP)-A and SP-D in semiquant ifying the extent of disease in IPF and in predicting deterioration in rest rictive pulmonary function and survival over a follow-up period of 3-yr. SP -A and SP-D in sera were measured with enzyme-linked immunosorbent assays a s previously described. Fifty-two IPF patients were studied to evaluate the association between serum SP-A and SP-D and disease extent on HRCT, deteri oration in pulmonary function, and survival during 3 yr of follow-up. Both SP-A and SP-D concentrations were significantly correlated with the extent of alveolitis (a reversible change), whereas they did not correlate with th e progression of fibrosis (an irreversible change). The SP-D concentration, unlike that of SP-A, was also related to the extent of parenchymal collaps e and the rate of deterioration per year in pulmonary function. The concent rations of SP-A and SP-D in patients who died within 3 yr were significantl y higher than in patients who were still alive after 3 yr. We propose that assays of SP-A and SP-D in sera from IPF patients are useful tools for unde rstanding some pathologic characteristics of the disease, that SP-D may be a good predictive indicator of the rate of decline in pulmonary function, a nd that a combination of the assays for SP-A and SP-D may be helpful in pre dicting the outcome of patients with IPF.