6.1. Study population

The study population comprised a total of 160 patients, of whom 120 underwent bronchofiberoscopy and bronchoalveolar lavage because of symptoms and/or findings suggestive of interstitial lung disease or minor changes in chest radiographs subsequent to asbestos exposure. These patients constituted a clinically representative sample of patients with sarcoidosis (Pietinalho et al.1995) and fibrosing alveolitis (Scott et al. 1990, Coultas et al. 1994). Five (25%) of the sarcoidosis patients with parenchymal involvement had been previously diagnosed and two of them (10%) were on oral corticosteroid medication. The BAL-procedure was performed to estimate the current activity of the disease as compar­able to a new case. All of the sarcoidosis patients without parenchymal changes were newly diagnosed. None of the patients in the fibrosing alveolitis group or with asbestos exposure had had prior medication for pulmonary disease. The sarcoidosis patients were younger and the fibrosing alveolitis patients older than the controls in this study, which is in line with the fact that sarcoidosis is more common in younger and fibrosing alveolitis in older populations (Coultas et al. 1994, Pietinalho et al.1995). The mean age of the asbestosis patients was 55 years and that of the asbestos exposure patients 54 years. This is in agreement with the latency of 15-20 years before asbestosis or pleural changes develop after the beginning of exposure (Becklake 1976) . The Ethics Committee of Päivärinne Hospital recommended avoidance of any additional procedures not necessary for the diagnosis or treatment of the patients. Because of this, the control group comprised 17 patients who had been examined because of minor respiratory symptoms, and there were no healthy controls.

The BALF and serum levels of procollagen I carboxyterminal and III aminoterminal propeptides were analysed from these 120 patients and 17 controls. At the time of the serum and BALF analyses, no method for procollagen I aminoterminal propeptide was available.

A sample of 23 patients were obtained from the pathology files of the Department of Pathology, University of Oulu, Finland. The files were searched for typical histopatholo­gical diagnoses of sarcoidosis or usual interstitial pneumonia. The clinical data were obtained from the case histories. The open lung biopsies were stained immuno­histo­chemically for procollagen I and III aminoterminal propeptides. Antibodies for procollagen I carboxyterminal propeptide were not available at the time of the immunohistochemical study.