Simultaneous measurement of collagen type-VI-related antigen and procollagen type-III-N-propeptide levels in bronchoalveolar lavage.

Abnormal collagen metabolism is a hallmark of diffuse lung disease. Biochemical parameters which are correlated with collagen synthesis and degradation may be helpful to monitor fibrosis. In this study, we compared the sensitivity and specificity of procollagen type-III-N-propeptide (PIIINP) and collagen type-VI (C-VI) related antigen levels, as well as a ratio of both parameters (PIIINP/C-VI), in bronchoalveolar lavage fluid (BALF) from patients with diffuse and localized lung disease. We investigated 45 patients with diffuse lung disease (idiopathic pulmonary fibrosis (IPF), n-21; samoidosis, n=13; and lymphangitic carcinomatosis (LC), n=11); 58 control subjects; and 92 patients with localized lung disease (bronchial carcinoma, n=37; pulmonary tuberculosis, n-31; and pneumonia, n=24). C-VI and PIIINP were measured by immunoassay in concentrated BALF. Although the PIIINP and C-VI levels were increased in diffuse lung disease, the sensitivity of the individual parameters PIIINP and C-VI was low (IPF: PIIINP=0.62, C-VI=0.29; LC: PIIINP=0.64, C-VI=0.45; samoidosis: PIIINP=0.69, C-VI=0.15). When calculating the ratio of PIIINP/C-VI for each individual patient, we found a significant increase in this ratio in IPF (1.28 +/- 0.7), LC (2.34 +/- 1.2), and samoidosis (0.26 +/- 0.08) compared to both the controls (0.02 +/- 0.01) and other localized lung diseases (bronchial carcinoma 0.05 +/- 0.01; pulmonary tuberculosis 0.02 +/- 0.01), with the exception of pneumonia (0.18 +/- 0.06). A ratio for PIIINP/C-VI greater-than-or-equal-to 0.03 was sufficiently specific (specificity in controls 0.88; in tuberculosis 0.87; and in bronchial cancer 0.79) and more sensitive (sensitivity in IPF 0.86; in sarcoidosis 0.85; and in LC 0.82) than each individual parameter. Simultaneous measurement of C-VI and PIIINP in BALF from patients with diffuse chronic lung diseases may be a more sensitive approach to assess disturbances in collagen metabolism than the determination of each single parameter.