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

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.