Comparison of exposure assessment methods for occupational carcinogens in a multi-centre lung cancer case-control study

Our plain-English summary of Comparison of exposure assessment methods for occupational carcinogens in a multi-centre lung cancer case-control study, by S. Peters, R. Vermeulen, A. Cassidy, et al (Occupational and Environmental Medicine, 2011).

The study

• Authors: S. Peters, R. Vermeulen, A. Cassidy, A. Mannetje, M. van Tongeren, P. Boffetta, K. Straif, H. Kromhout, INCO Group
• Journal: Occupational and Environmental Medicine
• Published: 2011;68(2):148-53
• Cited by: 83 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: Retrospective exposure assessment remains a problematic aspect of population-based case-control studies. Different methods have been developed, including case-by-case expert assessment and job-exposure matrices (JEM). The present analyses compare exposure prevalence and risk estimates derived by different exposure assessment methods.

Methods: In the context of a case-control study conducted in seven European countries, exposure was estimated for asbestos, diesel motor emissions (DME) and crystalline silica, using three different assessment methods. First, experts assigned exposures to all reported jobs on a case-by-case basis. Second, a population-specific JEM (PSJEM) was developed using the expert assessments of controls only, and re-applied to all study subjects. Third, an independent general population JEM (GPJEM) was created by occupational exposure experts not involved in the original study, and applied to study subjects. Results from these methods were compared.

Results: There was poor to fair agreement in assigned exposure between expert assessment and the GPJEM (kappas: asbestos 0.17; DME 0.48; silica 0.38). Exposure prevalence was significantly heterogeneous (p<0.01) between countries for all three agents and assessment methods. For asbestos and DME, significant country heterogeneity in risk estimates was observed when using expert assessment. When applying the GPJEM, the heterogeneity in risk estimates for asbestos and, to some extent, silica diminished.

Conclusions: It has been previously advocated that the expert assessment approach to assign exposures based on detailed questionnaire responses provides more accurate exposure estimates than JEM-based results. However, current results demonstrated little, if any, advantage of case-by-case assessment when compared to a JEM approach.

In plain English

This study used data from the INCO Copernicus lung cancer case-control study in six Central and Eastern European countries and the United Kingdom. It compared three ways of judging whether past jobs involved exposure to asbestos, diesel motor emissions or crystalline silica. The analysis covered 4784 people (2410 lung cancer cases and 2374 controls) recruited between 1998 and 2002. The three methods were case-by-case expert judgement, a job-exposure matrix built from experts' ratings of controls, and an independent general population matrix (the DOM-JEM). For asbestos, agreement between the experts and the DOM-JEM was poor (kappa 0.17). The DOM-JEM classed far more job periods as exposed to asbestos: 26% overall, versus 7% by experts. The overall odds ratio for lung cancer with asbestos exposure was 1.12 (95% CI 0.93 to 1.37) with expert assessment and 1.19 (1.05 to 1.36) with the DOM-JEM. Only the DOM-JEM result was statistically significant, and it varied less between countries. The authors concluded that case-by-case expert assessment offered minimal advantage over a general population matrix, which was faster and cheaper.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Methods comparison within a multi-centre lung cancer case-control study. Three exposure assessment methods were compared: case-by-case expert assessment, a population-specific job-exposure matrix (PSJEM) and a general population job-exposure matrix (GPJEM, called the DOM-JEM).
• Who was studied: 4784 subjects: 2410 lung cancer cases and 2374 controls, with 15 233 job periods. Subjects came from the Czech Republic, Hungary, Poland, Romania, Russia, Slovakia and the UK and were recruited 1998 to 2002. They made up 80% of the 5979 recruited.
• Exposure: Occupational exposure to asbestos (fiber type not specified in the assessment), diesel motor emissions (DME) and crystalline silica. Exposure was assigned to each job period and analysed as exposed versus non-exposed.
• Main results:
  • Overall agreement between expert ratings and the DOM-JEM was poor for asbestos (kappa 0.17) and silica (kappa 0.38), and fair to good for DME (kappa 0.48).
  • Percentage of job periods rated exposed to asbestos, by method:
• Overall: 7% by expert assessment, 8% by the PSJEM and 26% by the DOM-JEM.
• Central and Eastern European countries together: 5%, 6% and 25%.
• UK: 21%, 20% and 35%.
  • Most disagreement on asbestos was for miners and armed forces. In these groups only the DOM-JEM assigned asbestos exposure for several job types.
  • Overall odds ratios for lung cancer with ever exposure to asbestos:
• Expert assessment: 1.12 (95% CI 0.93 to 1.37).
• PSJEM: 1.04 (0.86 to 1.26).
• DOM-JEM: 1.19 (1.05 to 1.36).
  Only the DOM-JEM estimate was statistically significant.
  • Heterogeneity of asbestos risk estimates between countries:
• Expert assessment: p=0.0211.
• PSJEM: p=0.0263.
• DOM-JEM: p=0.4362, meaning the DOM-JEM results varied less between countries.
  • With expert assessment, the UK asbestos odds ratio was 2.23 (95% CI 1.36 to 3.67). When the UK was excluded, heterogeneity for expert-assessed asbestos decreased (p=0.27), so the UK accounted for most of the heterogeneity.
  • The authors interpreted the expert-versus-PSJEM agreement for asbestos (kappa 0.53, lower than for DME at 0.81 and silica at 0.70) as showing that expert asbestos ratings relied more on specific circumstances than on job title.
  • Overall silica odds ratios were statistically significant with all three methods: 1.26 (1.10 to 1.44) expert, 1.24 (1.08 to 1.43) PSJEM and 1.26 (1.08 to 1.47) DOM-JEM. Overall DME odds ratios (1.08, 1.05 and 1.05) were not statistically significant.
  • The authors argued that the absence of an asbestos lung cancer risk in the Central and Eastern European countries might have been caused by exposure misclassification. That absence had been discussed in earlier work on this study in connection with predominant chrysotile use there.
• The authors' conclusion: The authors concluded that the theoretical advantages of case-by-case expert assessment in a multi-centre study might be minimal. In their view, similar overall results with less heterogeneity could have been obtained faster and more cheaply with an external general population job-exposure matrix.
• Limitations the authors state:
  • True exposures were unknown, so the sensitivity and specificity of the methods could not be calculated.
  • The findings come from one multi-centre study. It is unknown how far they generalise to other studies, other experts or other general population matrices.
  • Job-exposure matrices cannot account for differences in exposure within the same job.
  • Time trends in exposure levels were not considered in the matrices.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer.

Medical terms in this study, explained in our Lexicon: Lung Cancer, Case-Control Study, Crystalline, Occupational Exposure.

Related studies

• Development of an exposure measurement database on five lung carcinogens (ExpoSYN) for quantitative retrospective occupational exposure assessment — S. Peters, R. Vermeulen, et al. (2012)
• Lung Cancer Risks Associated with Occupational Exposure to Pairs of Five Lung Carcinogens: Results from a Pooled Analysis of Case-Control Studies (SYNERGY) — A. Olsson, L. Bouaoun, et al. (2024)
• Comparison of expert and job-exposure matrix-based retrospective exposure assessment of occupational carcinogens in The Netherlands Cohort Study — N.S. Offermans, R. Vermeulen, et al. (2012)
• Cancer diagnosis in first-degree relatives and non-small cell lung cancer risk: results from a multi-centre case-control study in Europe — A. Cassidy, J. Balsan, et al. (2009)
• Comparison of exposure assessment methods in a lung cancer case-control study: performance of a lifelong task-based questionnaire for asbestos and PAHs — E. Bourgkard, P. Wild, et al. (2013)
• SYN-JEM: A Quantitative Job-Exposure Matrix for Five Lung Carcinogens — S. Peters, R. Vermeulen, et al. (2016)

Browse more research in Occupational and Environmental Medicine, or return to medical research.