Lavage type III procollagen N-terminal peptides in human pulmonary fibrosis and sarcoidosis.

Levels of type III procollagen N-terminal peptide were immunoassayed in sera and bronchoalveolar lavage fluids from healthy volunteers and patients with idiopathic pulmonary fibrosis or sarcoidosis. Peptide levels normalized to protein were higher than corresponding serum levels in all groups, suggesting that the lung is a producer of this peptide. Levels were significantly elevated in both patient groups, suggesting increased rates of type III collagen synthesis. Values were highest in idiopathic pulmonary fibrosis samples. Correlation of peptide levels with clinical severity of disease and lavage cell profiles was poor, perhaps because the latter reflects aspects of the disease process other than that stage in which type III collagen synthesis is altered. Lavage analyses of procollagen peptides may provide an important index of altered collagen synthesis in interstitial lung disease.