Background-Open lung biopsy is often performed to confirm the diagnosis in patients with suspected fibrosing alveolids. The superior sensitivity and specificity of high resolution computed tomography (CT) over chest radiography in various diffuse lung diseases suggest that the characteristic appearance of fibrosing alveolitis on high resolution CT might render biopsy confirmation unnecessary. Methods-The chest radiographs and high resolution CT scans of 86 patients (41 with fibrosing alveolitis and 45 with various other diffuse lung diseases) were examined individually and independently by two observers. No clinical information was given and the observers gave a level of confidence when the diagnosis was thought to be fibrosing alveolitis. Results-The observers correctly and confidently discriminated between fibrosing alveolitis and other diffuse lung diseases on high resolution CT with an accuracy of 88% and on chest radiography with an accuracy of 76%. The false negative rate for fibrosing alveolitis diminished from 29% on chest radiography to 11% on high resolution CT. The false positive rate on chest radiography was 190/o and on high resolution CT 13%; the false positive diagnoses on CT were the result of a few conditions (extrinsic allergic alveolitis, sarcoidosis, cryptogenic organising pneumonia, and pulmonary eosinophilia) which mimicked some of the CT features of fibrosing alveolitis. The superficial similarity of the CT patterns of these conditions are discussed. Conclusions-High resolution CT is superior to chest radiography in establishing the diagnosis of fibrosing alveolitis and the typical CT appearances are virtually pathognomonic. The diagnostic advantages of CT over chest radiography should further reduce the need for open lung biopsy in this condition. (Thorax 1993;48:334-338)
The clinical management of cryptogenic fibrosing alveolitis presents difficulties because both the prognosis and the response to treatment vary considerably in different patients.' Recent research into this condition has therefore attempted to find markers of disease activity and methods of predicting the response to treatment, so that patients who need treatment can be treated promptly and appropriately.On the basis of histological studies excess collagen production has been assumed to be an essential feature of cryptogenic fibrosing alveolitis, but this has not been biochemically proved.2 Recently, interest in the role of collagen in cryptogenic fibrosing alveolitis has been revived by the finding of several
To assess the role of changes in lung collagen in pulmonary fibrosis, the content of this protein was measured in biopsy and autopsy lung from patients with cryptogenic fibrosing alveolitis (CFA), a fibrotic lung disorder of unknown cause. The collagen concentration was measured in lung samples from 21 patients with CFA (14 autopsy and seven open-lung biopsy) and 17 normal subjects; total lung collagen was determined in the right lung of 10 patients who died from CFA and the results were compared with those from 10 normal lungs. There was a wide variation in the collagen concentrations but the mean value (+/- SEM) for patients with CFA (217 +/- 13 mg/g dry weight) was significantly higher (P less than 0.02) than that of the controls (155 +/- 15 mg/g dry weight). The mean collagen concentration of the autopsy samples (243 +/- 20 mg/g dry weight) was significantly higher (P less than 0.05) than that of the biopsy samples (165 +/- 24 mg/g dry weight). The mean total collagen was markedly raised (P less than 0.001) in right lungs of patients with CFA (32.5 +/- 4.3 g) compared with normal lungs (14.0 +/- 1.1 g). When corrected for the predicted lung volume this difference in total lung collagen remained statistically significant (P less than 0.01, mean for patients 4.7 +/- 0.7 mg/ml, controls 2.3 +/- 0.2 mg/ml). These results demonstrate an increased deposition of lung collagen in this form of pulmonary fibrosis. They also suggest that there is a greater collagen concentration in lungs of patients with later disease, indicating a progressive deposition of collagen during the course of the disease.
Serum levels of the amino-terminal type III procollagen peptide (P-3-NP) have been used as an index of collagen synthesis. Systemic sclerosis (SS) is characterized by uncontrolled production of collagen of several types. This study aimed to explore the profile of P-3-NP in patients with SS and Raynaud's phenomenon, a common forerunner of the disease. Using a radioimmunoassay, the mean level for P-3-NP was found to be raised in SS compared with both the control (p less than 0.001) and Raynaud's groups (p less than 0.001). Analysis of serial samples from the patients with SS suggested that the P-3-NP level reflected changing clinical activity. Three groups emerged: a group with stable disease which showed a less than 20% change in P-3-NP level (mean 5.7%); a group with increasing activity which showed an increase of greater than 20% (mean 35.8%) and a group of decreasing activity which showed a decrease of greater than 20% (mean 33.6%). These data suggest that there is an increase in collagen metabolism in SS and that changes in P-3-NP levels may reflect the clinical course of the disease.
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