Asbestos bodies or fibers and the diagnosis of asbestosis.

A committee of the College of American Pathologists has proposed that the diagnosis of asbestosis requires fibrosis in respiratory bronchiolar walls and the presence of asbestos bodies (ABs) in tissue sections. To determine whether histologic ABs reliably reflect asbestos fiber concentrations in asbestosis, we compared the concentration of ABs in histologic sections to concentrations of ABs and fibers in tissue extracts of 14 asbestos workers with nonspecific interstitial fibrosis. ABs in histologic sections and extracts correlated well, r = 0.95. Counted and classified by electron microscopy, electron diffraction, and X-ray spectroscopy, commercial amphibole fibers (r = 0.94) also correlated well with ABs, but noncommercial amphiboles (r = -0.02) or chrysotile (r = 0.29) did not. In five subjects with a high percentage of noncommerical amphibole fibers, fewer than 0.5 histologic ABs/cm2 were present despite a total amphibole concentration that was similar to that in subjects with more histologic ABs. We conclude that ABs will be scarce or absent in histologic sections from some subjects with asbestosis, and that for such subjects, extracts of asbestos fibers should yield over 500,000 total amphibole fibers/g dry lung to signify that interstitial fibrosis may be caused by asbestos.