Relevance of asbestos bodies in sputum

Abstract

The presence of asbestos bodies (ABs) in sputum specimens of individuals with occupational asbestos exposure has been well-documented. The aim of this study was to determine their clinical relevance in comparison to the concentration of AB in bronchoalveolar lavage (BAL) and lung tissue.Subjects were included following a well-documented exposure of asbestos history (n=93) or BAL fluid analysis positive for ABs (n=42). The subjects with a well documented history of AB exposure were divided into three groups: heavy (Group 1, n=29); moderate (Group 2, n=31); or occasional exposure (Group 3, n=33). BAL fluid was available from all subjects, and lung tissue from 21 subjects. To assess the variability, 10 sputum positive subjects collected subsequent sputum on days 2, 7, 14, 30 and 90. ABs were determined by light microscopy after membrane 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 ) suggesting a correlation with cumulative exposure. However, many negative sputum samples were noted, when BAL specimens were positive. The AB content of sputum and BAL specimens did not correlate. ABs were found in sputum of all subjects with a tissue content of >1,000 AB·cm -3 , but in none with contents of <1,000 AB·cm -3 . Substantial variability of ABs was found in the five sequentially collected sputa of 10 initially positive patients (coefficient of variation 28-93%), but only two false negatives were found in these 50 samples.Thus, sputum analysis for asbestos bodies is an insensitive method for assessing the lung asbestos burden, much less sensitive than bronchoalveolar lavage fluid analysis. However, a sputum sample positive for asbestos bodies is suggestive of a high lung asbestos burden.

Asbestos bodies in the sputum of asbestos workers: correlation with occupational exposure

“…In previous reports, the frequency of detection of asbestos bodies in sputum differed from one occupational cohort to another: in highly exposed subjects, FARLEY et al [11] and MACDONALD et al [10] reported 35% and 29% of positive analyses, respectively. In vermiculite miners, SEBASTIEN et al [9] detected asbestos bodies in the sputum of 75% of workers; TESCHLER et al [3] reported positive asbestos body counts in 36.5% of occupationally exposed subjects and SULOTTO et al [12] reported a rate of 44.4%.…”

“…In comparison with bronchoalveolar lavage, thoracoscopic or open lung biopsy, induced sputum has the obvious advantage of being a noninvasive method. Unfortunately, the sensitivity of asbestos bodies in sputum as a marker of asbestos exposure is poor, whereas a sputum sample positive for asbestos bodies suggests a significant lung asbestos burden [3]. The objective of this investigation, conducted in a population of retired workers from a plant manufacturing asbestos-containing products (textile and friction materials), was to study the correlation between the presence of asbestos bodies in the sputum of these subjects and the amount and mineralogical type of their asbestos exposure.…”

Guidelines for mineral fibre analyses in biological samples: report of the ERS Working Group. European Respiratory Society

“…At least three studies comparing LT and sputum AB contents indicated that AB do not appear in sputum below a lung burden in the order of 1000 AB·g -1 wet lung or more (approximately 10,000 AB·g -1 dry lung) [46]. A negative sputum sample for AB does not exclude the possibility of a high lung AB burden.…”

“…A high variation in AB counts has been demonstrated on sequential sputum samples, and analysis of pooled daily expectoration of sputum may yield fewer false-negative results [46,47], but even with five specimens the sensitivity remained quite low [48]. At least three studies comparing LT and sputum AB contents indicated that AB do not appear in sputum below a lung burden in the order of 1000 AB·g -1 wet lung or more (approximately 10,000 AB·g -1 dry lung) [46].…”

“…However, sputum AB content is a very insensitive measure of lung asbestos fibre burden. TESCHLER et al [46] found that sputum samples were positive in only 28, 43 and 79% of individuals with 1-4.9, 5-49.9 and more than 50 AB·mL -1 in BAL, respectively. The sputum samples were negative in 33% of heavily exposed, 68% of moderately exposed and 45% of occasionally exposed subjects with AB in BAL samples.…”