Interpretation and significance of pathologic findings in transbronchial lung biopsy.

We evaluated the pathologic features and clinical significance of 50 transbronchial lung biopsies from 45 immunosuppressed patients (Group I) and 41 from 39 nonimmunosuppressed patients (Group II). Specific diagnoses were established in only 36% of Group I, and of these two-thirds were infections. Expected inflammatory reactions to infection were absent in most of these immunosuppressed patients. Nonspecific pathologic changes were found in 40%, of which diffuse alveolar damage and interstitial pneumonitis were the most common. The mortality was highest for Group I patients with infections (50%) and with diffuse alveolar damage (56%). In Group II patients specific diagnoses were made in only 7%, although histologic abnormalities were found in an additional 61%. This study emphasizes several important differences which should be considered in evaluating transbronchial lung biopsies from immunosuppressed and nonimmunosuppressed patients. This biopsy procedure is most useful in diagnosing infection in immunosuppressed patients but the histology may be difficult to interpret since the usual inflammatory reactions are often absent. This procedure is also useful in evaluating nonimmunosuppressed patients, although open biopsy may be necessary when clinical and pathologic features do not correlate.