RELEVANCE OF ASBESTOS BODIES IN SPUTUM

The presence of asbestos bodies (ABs) in sputum specimens of individua ls with occupational asbestos exposure has been well-documented. The a im of this study was to determine their clinical relevance in comparis on to the concentration of AB in bronchoalveolar lavage (BAL) and lung tissue. Subjects were included following a well-documented exposure o f asbestos history (n=93) or BAL fluid analysis positive for ABs (n=42 ). The subjects with a well documented history of AB exposure were div ided into three groups: heavy (Group 1, n=29); moderate (Group 2, n=31 ); or occasional exposure (Group 3, n=33). BAL fluid was available fro m all subjects, and lung tissue from 21 subjects. To assess the variab ility, 10 sputum positive subjects collected subsequent sputum on days 2, 7, 14, 30 and 90. ABs were determined by light microscopy after me mbrane filtration of specimen digests. The mean sputum AB content was highest in Group 1 (2.4+/-5.5 AB . mL(-1)), lower in Group 2 (0.2+/-0. 3 AB . mL(-1)) and lowest in Group 3 (0.1+/-0.1 AB . mL(-1)) suggestin g a correlation with cumulative exposure. However, many negative sputu m samples were noted, when BAL specimens were positive. The AB content of sputum and BAL specimens did not correlate, ABs were found in sput um of all subjects with a tissue content of >1,000 AB . cm(-3), but in now with contents of <1,000 AB . cm(-3). Substantial variability of A Bs was found in the five sequentially collected sputa of 10 initially positive patients (coefficient of variation 28-93 %), but only two fal se negatives were found in these 50 samples. Thus, sputum analysis for asbestos bodies is an insensitive method for assessing the lung asbes tos burden, much less sensitive than bronchoalveolar lavage fluid anal ysis. However, a sputum sample positive for asbestos bodies is suggest ive of a high lung asbestos burden.