THE "GOLD STANDARD" FOR PAST ASBESTOS EXPOSURE

To the Editor :

We have been delighted that our article on asbestos-induced pleural plaques (1) was accompanied by an editorial (2). We thank Drs. Bégin and Christman for their appreciative comments. We obviously agree with most of their comments, in particular that detailed occupational histories should be taken when faced with asbestos-related lung disease. However, we have some problems with their statement that "the best indicator of past asbestos exposure (the gold standard) remains the detailed past work history." This is not what we intended to conclude from our study.

Why do we not agree that the past work history should be the gold standard for past asbestos exposure? The history is rarely, if ever, an accurate reflection of the level of exposure, particularly if this is obtained by questioning the patient, which is often the only available option. People sometimes ignore totally that they have ever been exposed to asbestos, either at work, or elsewhere; in addition, when they do know that they have worked with asbestos-containing materials, most are not capable of indicating how high their exposure has been. Clinical experience and a large body of published evidence (3) teaches us that substantial asbestos exposure may remain "occult," even after extensive questioning of the patient. On the other hand, some patients claim, or fear, that they have been exposed to huge quantities of asbestos, although their exposure has only been trivial.

Consequently, while we agree that a detailed occupational history is an essential cornerstone in the diagnosis of asbestos-related lung disease, we do not think that it can ever be the best indicator, let alone a gold standard. As is acknowledged in the editorial (2), quantitative assessments of fiber burden in lung tissue, and to some extent also in bronchoalveolar lavage (6), are generally more accurate indicators, although they too are not perfect, particularly to assess remote exposures to chrysotile. So, there is probably no gold standard to evaluate the degree of the past exposure to asbestos, and we are left with having to use combined approaches, including, of course, the occupational history. What we have shown (1) is that the total surface of small-to-moderate pleural plaques does not correlate well with the estimated cumulative exposure to asbestos (and this goes both ways, because low exposure may give large plaques and high exposure may give small plaques). Nevertheless, plaques remain a virtually pathognomonic hallmark of such exposure.

Laboratory of Pneumology (Unit of Lung Toxicology), Leuven, Belgium

1. Van Cleemput J, De Raeve H, Verschakelen J, Rombouts J, Lacquet LM, Nemery B. Surface of localized pleural plaques quantitated by computed tomography scanning. No relation with cumulative asbestos exposure and no effect on lung function. Am J Respir Crit Care Med 2001; 163: 705-710 [Abstract/Free Full Text].

2. Bégin R, Christman JW. Detailed occupational history. The cornerstone in diagnosis of asbestos-related lung disease. Am J Respir Crit Care Med 2001; 163: 598-599 [Free Full Text].

3. Quinn MM, Kriebel D, Buiatti E, et al . . An asbestos hazard in the reprocessed textile industry. Am J Ind Med 1987; 11: 255-266 [Medline].

4. Corhay JL, Delavignette JP, Bury T, Saint-Remy P, Radermecker MF. Occult exposure to asbestos in steel workers revealed by bronchoalveolar lavage. Arch Env Health 1990; 45: 278-282 [Medline].

5. De Vuyst P, Dumortier P, Gevenois PA. Analysis of asbestos bodies in BAL from subjects with particular exposures. Am J Ind Med 1997; 31: 699-704 [Medline].

6. De Vuyst P, Karjalainen A, Dumortier P, et al . . Guidelines for mineral fibre analyses in biological samples: report of the ERS Working Group. Eur Respir J 1998; 11: 1416-1426 [Abstract].

From the Authors:

We read with interest the letter from Dr. Van Cleemput and associates. The authors point to some difficulties encountered in obtaining an occupational history and remark that there are often discrepancies between the patient's exposure perception and the findings on lavage and tissue analyses.

We agree that in some circumstances it may be difficult to use occupational history to accurately evaluate cumulative past asbestos exposure and that lung fiber retention analyses on bronchoalveolar lavage or tissue analyses may provide additional useful information. We agree, but on one hand these latter tools are not without their own problems. On the other hand, the presence of pleural plaques on chest X-ray or CT scan is useful as markers of past exposure, particularly when bilateral. Van Cleemput and colleagues (1) have established that the surface of pleural plaques on CT scan does not correlate well with the estimated cumulative exposure to asbestos.

The objective of an editorial is not necessarily only to comment on an article that provides an interesting observation, but also to try to see that observation in the context of a larger scheme; this is what we have attempted to do in our editorial.

Université de Sherbrooke, Sherbrooke, Québec, Canada

1. Van Cleemput J, De Raeve H, Verschakelen J, Rombouts J, Lacquet LM, Nemery B. Surface of localized pleural plaques quantitated by computed tomography scanning. No relation with cumulative asbestos exposure and no effect on lung function. Am J Respir Crit Care Med 2001; 163: 705-710 .