Abstract Background Since the 1980s, lung fibre burden analysis has been used in reconstructing past exposure to asbestos and in estimating the dose–response relationship for asbestos-related cancers. Objective The objective of this study was to evaluate the validity (sensitivity and specificity) of the reference values proposed by the Helsinki Consensus Documents in 1997 and 2014 to assign asbestos exposure. Methods Counts of asbestos bodies (AB) and amphibole asbestos fibres (AAF) in dry lung tissue samples performed by the ARPA Electron Microscopy Laboratory in Milan from 2009 to 2020 have been used to assess the discriminating performance between asbestos exposure and background exposure. For each sample/individual, we retrieved information on disease diagnosis and on asbestos exposure at work or in other settings. We calculated sensitivity and specificity using either Helsinki criteria (1000+ AB or 1,000,000+ AAF 1 µm per gram of dry lung tissue) or different optimal statistical cut-points chosen on the basis of three statistical methods. Results From the original list of 822 samples, we selected samples from 563 individuals with information on disease (325 with mesothelioma, 158 with lung cancer, 24 with asbestosis or pleural plaques, and 56 without asbestos-related diseases) and with information on asbestos exposure. The number of subjects with a history of asbestos exposure was 507, 478 occupationally exposed and 29 with familiar or environmental exposure. The 56 individuals without asbestos-related diseases (of whom 53 were included in a previous publication on background asbestos exposure) were taken as “unexposed.” The estimated (rounded) optimal cut-points were 600 AB and 300,000 AAF with all three statistical methods. The Helsinki criteria had very good specificity (1 for AB and 0.95 for AAF), and good sensitivity (0.89) for AB, while sensitivity was quite low for AAF (0.67, implying one third of false negatives). The optimal statistical cut-points showed higher sensitivity for AB (0.94) and much better sensitivity for AAF (0.85). In sub-analyses, we found that the Helsinki criteria had good/sufficient sensitivity only among 249 highly exposed shipyard workers, not among 258 individuals with lower exposure; the optimal statistical cut-points yielded higher sensitivity, especially in lower-exposed individuals. Conclusions Based on a large sample size, we have shown good sensitivity for AB but very low sensitivity for AAF using Helsinki criteria for the attribution of exposure to asbestos. We propose to adopt lower values (600 AB or 300,000 AAF), because they would avoid a large proportion of false negatives. We remind that lung fibre burden analysis should be viewed as a complement (not a substitute) for a carefully collected lifetime job history.
Barbieri et al. (Fri,) studied this question.