title: Bayesian adjustment for measurement error in continuous exposures in an individually matched case-control study.
abstract: BACKGROUND
  In epidemiological studies explanatory variables are frequently subject to measurement error. The aim of this paper is to develop a Bayesian method to correct for measurement error in multiple continuous exposures in individually matched case-control studies. This is a topic that has not been widely investigated. The new method is illustrated using data from an individually matched case-control study of the association between thyroid hormone levels during pregnancy and exposure to perfluorinated acids. The objective of the motivating study was to examine the risk of maternal hypothyroxinemia due to exposure to three perfluorinated acids measured on a continuous scale. Results from the proposed method are compared with those obtained from a naive analysis.
  
  
  METHODS
  Using a Bayesian approach, the developed method considers a classical measurement error model for the exposures, as well as the conditional logistic regression likelihood as the disease model, together with a random-effect exposure model. Proper and diffuse prior distributions are assigned, and results from a quality control experiment are used to estimate the perfluorinated acids' measurement error variability. As a result, posterior distributions and 95% credible intervals of the odds ratios are computed. A sensitivity analysis of method's performance in this particular application with different measurement error variability was performed.
  
  
  RESULTS
  The proposed Bayesian method to correct for measurement error is feasible and can be implemented using statistical software. For the study on perfluorinated acids, a comparison of the inferences which are corrected for measurement error to those which ignore it indicates that little adjustment is manifested for the level of measurement error actually exhibited in the exposures. Nevertheless, a sensitivity analysis shows that more substantial adjustments arise if larger measurement errors are assumed.
  
  
  CONCLUSIONS
  In individually matched case-control studies, the use of conditional logistic regression likelihood as a disease model in the presence of measurement error in multiple continuous exposures can be justified by having a random-effect exposure model. The proposed method can be successfully implemented in WinBUGS to correct individually matched case-control studies for several mismeasured continuous exposures under a classical measurement error model.
authors.affiliation: Department of Statistics, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Espino-Hernandez
authors.forename: Paul
authors.initials: P
authors.lastname: Gustafson
authors.forename: Igor
authors.initials: I
authors.lastname: Burstyn
mesh_terms: D001499:Bayes Theorem; D016022:Case-Control Studies; D003627:Data Interpretation, Statistical; D005260:Female; D005466:Fluorocarbons / Q000009:adverse effects; D006801:Humans; D007037:Hypothyroidism / Q000139:chemically induced / Q000453:epidemiology*; D011247:Pregnancy; D012306:Risk; D013963:Thyroid Hormones / Q000097:blood
chemical_list: D005466:Fluorocarbons; D013963:Thyroid Hormones