Exposure assessment for a population-based case-control study combining a job-exposure matrix with interview data

Objectives A system that combines the ease of use of a job-exposure matrix while taking into account jobspecific data is needed. This study aimed to produce a detailed method for combining interview data with expert assessments for a large population-based case-control study of Parkinson’s disease. Method An interview-administered core questionnaire with a series of questions that triggers substance-specific questionnaires to gather information on key parameters is administered. Using a job-exposure matrix to generate base estimates, assessors can modify this estimate of exposure intensity using worker-specific data such as the use of control measures, reports of substance-specific acute symptoms, and the quantity of material being processed. Detailed guidance for making adjustments to exposure estimates for these modifiers is presented. Results The method has been partially validated through the use of a comparison of estimates for a separate cohort with previously validated exposure reconstructions. Agreement was high, with a Spearman’s rho of 0.89 (P<0.01). The results from a quality assurance system employed as part of the methodology show a high degree of repeatability in generated exposure values both over time (Spearman's rho 0.98, P<0.01) and between different assessors (Spearman's rho 0.88, P<0.01). Conclusions The method provides detailed quantitative exposure indices for occupational epidemiology. It has particular strengths both in terms of ease and speed of use. It is hoped that it will provide a useful structure for future epidemiologic work.