4.1. Study population

The study included 160 patients investigated because of suspected interstitial lung disease or asbestos exposure. Altogether 137 consecutive patients were admitted to the pulmonary departments of Päivärinne Hospital (Muhos, Finland) between February 1990 and August 1992 (I-III). The patients came from the province of Oulu in Northern Finland and had been referred to investigations mostly by general practitioners. These 137 patients underwent bronchofiberoscopy and bronchoalveolar lavage due to their symptoms and findings. The study was performed as part of the normal diagnostic procedures and the serum and BALF samples were split off from routine specimens. The clinical data, including the laboratory results and pulmonary function tests, were obtained from the case histories. The remaining 23 patients had undergone open lung biopsies between 1981 and 1998 (IV). Pulmonary specialists from the pulmonary clinics of Northern Finland had referred these patients to open lung biopsies. Their paraffin blocks of biopsy specimens were obtained from the pathology files at the Department of Pathology, University of Oulu, Finland, and the clinical data were obtained from the case histories.

Sixty patients out of the 137 were diagnosed as having sarcoidosis (I). Forty of them had non-parenchymal sarcoidosis (Stage 0-I in chest radiography), and 20 were con­sidered to have parenchymal involvement (Stage II-III in chest radiography). No visible changes in radiography were considered stage 0. Nodular hilar enlargement was the criterion for hilar adenopathy (Stage I). Reticular, nodular and/or linear patterns were criteria for parenchymal involvement (Fraser et al. 1994). All the patients in the former group were newly diagnosed, whereas five patients in the latter group had been formerly diagnosed as having sarcoidosis and two of them were on oral corticosteroid medication at the time of diagnosis. Histological confirmation of diagnosis was available for 35 patients with biopsies taken either transbronchially, via mediastinoscopy, from superficial lymph nodes or from the skin. Typical sarcoidosis changes were seen in 16 of the parenchymal and 19 of the non-parenchymal patients. In the remaining 25 cases the diagnosis was based on a typical clinical picture, marked lymphocytosis in BALF and typical findings in chest radiography as well as exclusion of other diseases. The clinical characteristics of the sarcoidosis patients are presented in table 2.

Fibrosing alveolitis was diagnosed in 18 of the 137 patients (II). Biopsies in 9 patients and autopsy in one patient confirmed the diagnosis. The diagnosis of the remaining 8 patients based on typical findings in chest radiography, BALF, spirometry and diffusion capacity, and the exclusion of other pulmonary diseases. Sixteen of these 18 patients were considered to have idiopathic fibrosing alveolitis, one patient had rheumatoid arthritis and one had scleroderma with pulmonary involvement. The mean follow-up time of these patients was 6 years and 2 months (range between 5 and 7 years). The clinical charac­teristics of the fibrosis patients are shown in table 2.

Forty-two patients were referred to investigations due to a history of occupational asbestos exposure and changes in chest radiography (III). The radiological changes included either pleural plaques or an interstitial basal reticular-linear pattern suggestive of fibrosis and asbestosis. Five patients were diagnosed as having asbestosis, 25 had pleural plaques, and the chest radiographs of 12 patients were considered normal. In one patient the asbestosis diagnosis was based on an open lung biopsy. The remaining 4 patients with asbestosis had typical findings in chest radiography, spirometry and diffusion capacity and a significant but variable amount of asbestos bodies in BALF. Other pulmonary diseases were excluded. The mean follow-up time was 7 years (from 5 years 7 months to 7 years 10 months). The characteristics of the asbestos-exposed individuals are presented in table 3.

The control group (I-II) consisted of 17 subjects who underwent fiberoptic broncho­scopy because of prolonged cough, haemoptysis or other minor respiratory symptoms. Four of the patients were later considered asthmatic. There were no changes in the chest radiographs of this group. The characteristics of the control group are shown in table 2.

The Ethics Committee of Päivärinne Hospital approved the research protocol. Informed consent was obtained from each subject beforehand.

Twenty-three patients who had undergone open or thoracoscopic lung biopsy (IV) were drawn from the files of the Department of Pathology, University of Oulu. Histopathologically typical 10 cases with fibrosing alveolitis and 13 cases with sarcoidosis were re-evaluated. The diagnoses of the patients were based on light-microscopic evaluations using the previously described histological criteria (Dail & Hammer 1994, Thurlbeck & Churg 1995, Katzenstein 1997). The patients’ histological biopsies were investigated immunohistochemically. The clinical characteristics of the sarcoidosis patients are presented in table 4 and those of the fibrosing alveolitis patients in table 5.