False positive exposure errors and low exposure prevalence in community-based case-control studies.
Appl Occup Environ Hyg 1991 Jun; 6(6):534-540
A discussion was presented of quantification of bias to the odds ratio due to nondifferential exposure misclassification under a range of conditions common to community based case control studies. In such studies, exposure prevalence was commonly low. Bias to the odds ratio was defined in terms of excess risk between true and observed odds ratios and was positive for risk overestimation and negative for risk underestimation. Nondifferential errors always caused underestimation of true odds ratios. The magnitude of such errors depended on proportion of comparisons exposed, sensitivity and specificity. For low exposure prevalence (less than 10%), false negative classification errors resulted in negligible bias while most bias was attributable to false positive errors. Main error sources included respondent, data coding and exposure assessment. Causes of such errors, their effects on subject classification and strategies to reduce any subsequent bias were reviewed. Respondent errors included omission or false report of an occupation or inaccurate or vague occupation information. Coding errors included within and between coder inconsistency, inadequate occupation information for coding certainty and code heterogeneity with respect to exposure status. Exposure assessment errors included false exposure designation of a job title and arbitrary assignment of exposure for a job title. Recommended strategies for minimizing effects of false positive errors included using exposure groups rather than occupational title groups for analysis, repeat interviews of subjects classified as exposed and research on methods used to obtain occupational histories and to assess exposures. The authors conclude that improving quality of occupational case referent study data requires a concerted resource investment into understanding current methods and developing new methods.
NIOSH-Publication; NIOSH-Contract; Contract-91-38661; Case-studies; Exposure-levels; Health-surveys; Occupational-exposure; Occupational-health; Quantitative-analysis; Analytical-methods
Applied Occupational and Environmental Hygiene