Context: Asbestosis is one of many forms of diffuse interstitial pulmonary fibrosis. Its histologic diagnosis rests on the pattern of fibrosis and the presence of asbestos bodies by light microscopy in lung biopsies.
Objective: To determine the asbestos fiber burden in patients with diffuse pulmonary fibrosis (DPF) who had a history of asbestos exposure, but whose biopsies did not meet established criteria for asbestosis, and compare it with the fiber burden in confirmed asbestosis cases.
Design: Fiber burden analysis was performed using scanning electron microscopy and energy-dispersive x-ray analysis of lung parenchyma from 86 patients with DPF and 163 patients with asbestosis. The correlation of the number of asbestos fibers found for a quantitative degree of fibrosis was analyzed.
Results: The fibrosis scores of the asbestosis cases correlated best with the number of uncoated commercial amphibole fibers. Seven DPF cases fell within the 95% interval of asbestos body count by light microscopy and 3 cases within that of the total commercial amphibole fiber count.
Conclusions: Strict histologic criteria are useful for positive identification of asbestosis among cases of advanced pulmonary fibrosis. Few DPF patients with history of asbestos exposure whose biopsies did not meet the criteria for asbestosis may have asbestos fiber counts in the range seen in asbestosis, and fiber type identification by scanning electron microscopy with energy-dispersive x-ray analysis should be considered in these rare instances to avoid false-positive and false-negative diagnoses of asbestosis.