A comparison of exposure assessment approaches: lung cancer and occupational asbestos exposure in a population-based case-control study

Our plain-English summary of A comparison of exposure assessment approaches: lung cancer and occupational asbestos exposure in a population-based case-control study, by J.S. Hardt, R. Vermeulen, S. Peters, et al (Occupational and Environmental Medicine, 2014).

The study

• Authors: J.S. Hardt, R. Vermeulen, S. Peters, H. Kromhout, J.R. McLaughlin, P.A. Demers
• Journal: Occupational and Environmental Medicine
• Published: 2014;71(4):282-8
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: In attempts to overcome the limitations of self-reported data in occupational health research, job-exposure matrices, which assign exposure by occupation, have emerged as an objective approach for assessing occupational exposures. On the basis of a lung cancer case-control study conducted in the Greater Toronto Area, 1997-2002, assessment of occupational exposure to asbestos was compared using self-reports and a general population job-exposure matrix (DOM-JEM).

Methods: Cases and frequency matched controls provided life-time job histories and self-reported exposures to potential lung carcinogens including asbestos through a detailed questionnaire. Exposure to asbestos was also assigned to each job by linking occupational histories with DOM-JEM. Agreement in classification of exposed and unexposed jobs according to self-reports and DOM-JEM was evaluated using Cohen's κ. Risks for lung cancer were estimated using unconditional logistic regression for each exposure assessment approach.

Results: The prevalence of occupational asbestos exposure was greater when based on DOM-JEM than when based on self-reports. Agreement in classifying exposure to jobs between the two assessment approaches was poor. The risk of lung cancer was not elevated among workers who self-reported asbestos exposure, whereas workers considered exposed on the basis of DOM-JEM were almost twice as likely as unexposed workers to be diagnosed with lung cancer (OR 1.9, 95% CI 1.3 to 2.7).

Conclusions: It is generally assumed by epidemiologists that self-reported exposure assessments result in inflated risk estimates. In this study, self-reports found no association with a well-established risk factor, whereas a high-quality job-exposure matrix revealed relative risk estimates that are more consistent with previous findings.

In plain English

This population-based case-control study from the Greater Toronto Area compared two ways of measuring past workplace asbestos exposure in 425 people with lung cancer, diagnosed 1997 to 2002, and 910 cancer-free controls. Participants were asked whether they had ever worked with asbestos in any job. Separately, the authors rated each job as having no, low or high asbestos exposure using a job-exposure matrix called DOM-JEM. The article does not name fiber types. By self-report, 82 participants (6%) were exposed. By DOM-JEM, 194 (15%) were. Agreement between the two methods was poor (kappa 0.19). Results were adjusted for age, sex and smoking. Self-reported exposure was not associated with lung cancer (odds ratio 0.9, 95% CI 0.5 to 1.6). People classed as exposed by DOM-JEM had nearly twice the odds of unexposed people (OR 1.9, 95% CI 1.3 to 2.7), and those in exposed jobs for more than 10 years had an OR of 2.6 (95% CI 1.5 to 4.5). The authors concluded that DOM-JEM gave a more accurate measure of exposure. They noted that no true gold standard exists for comparison.

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: Population-based lung cancer case-control study comparing two exposure assessment methods: self-report and a general population job-exposure matrix (DOM-JEM)
• Who was studied: 425 cases of cancer of the trachea, bronchus or lung, aged 20 to 84, identified 1997 to 2002 through four tertiary care hospitals in metropolitan Toronto. They were compared with 910 cancer-free controls: population controls drawn from property tax assessment files and hospital controls from Mount Sinai Hospital Family Medicine Clinic. Controls were frequency matched on age, sex and ethnicity.
• Exposure: Occupational asbestos exposure (fiber type not specified), assessed two ways. Participants answered one questionnaire item on whether they had ever worked with asbestos. Separately, each job was linked by ISCO-68 occupation code to DOM-JEM, which assigned no, low or high exposure. Duration was the number of years in jobs classed as exposed.
• Main results:
  • Across all participants, 82 (6%) were exposed by self-report, compared with 194 (15%) by DOM-JEM.
  • Self-reported exposure did not differ significantly between cases and controls (7% vs 6%, p=0.23). By DOM-JEM, cases were much more likely than controls to be classed as exposed (23% vs 11%, p less than 0.0001).
  • Agreement between self-reports and DOM-JEM in classing each job as exposed or unexposed was poor (kappa 0.19 overall). Agreement was 0.25 in controls and 0.12 in cases, and highest for construction jobs (0.30).
  • Among participants whose two assessments disagreed for at least one job (17% of participants), 22% reported exposure that DOM-JEM did not assign. The other 78% did not report exposure that DOM-JEM assigned. Of 69 individuals ever employed in construction, over 40% did not report exposure that DOM-JEM assigned in one or more construction jobs.
  • Self-reported asbestos exposure was not associated with an increased risk of lung cancer (OR 0.9, 95% CI 0.5 to 1.6). Estimates were adjusted for age group, sex and smoking pack-years, with a 10-year lag.
  • People classed as exposed by DOM-JEM had a nearly twofold increased risk of lung cancer compared with those classed as unexposed (OR 1.9, 95% CI 1.3 to 2.7).
  • By DOM-JEM, people ever employed in a high-exposure job had an OR of 2.3 (95% CI 0.8 to 6.5). People employed only in low-exposure jobs had an OR of 1.9 (95% CI 1.2 to 2.6).
  • By DOM-JEM, more than 10 years in exposed jobs was associated with an OR of 2.6 (95% CI 1.5 to 4.5). Ten years or fewer was associated with an OR of 1.5 (95% CI 0.9 to 2.4), both compared with the unexposed group.
• The authors' conclusion: The authors concluded that DOM-JEM gave a more accurate measure of asbestos exposure than self-reports. They also stated that null results from studies using only self-reports should be treated as inconclusive.
• Limitations the authors state:
  • There is no true gold standard method for past asbestos exposure assessment against which to compare self-reports and DOM-JEM.
  • Participants with incomplete data collection were excluded, and next-of-kin were not interviewed.
  • The study was limited to asbestos, so the differences between methods may not extend to other exposures.
  • The self-report question may have missed exposure from working near, but not directly with, asbestos.
  • DOM-JEM assumes everyone in an occupational group has the same exposure. It also does not capture historical changes in asbestos use, processes or safety measures.

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, Asbestos Exposure, Case-Control Study, Occupational Exposure, Relative Risk.

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