An empirical investigation of exposure measurement bias and its componentsin case-control studies

This study investigated bias due to misclassification of exposure in case c ontrol studies. Using a metaanalysis of data from a number of case control studies, in which a possibly misclassified exposure was validated against a more reliable one, estimates of misclassification indices and bias were ob tained. The estimates were used to investigate whether misclassification in dices, in particular, sensitivity and specificity and so-called quality ind ices, are typically nondifferential with respect to cases and controls. It is concluded that quality indices do not show any tendency to be either low er or higher in cases than controls. On the other hand, sensitivity tends t o be higher in cases than controls and specificity lower. Estimates of misc lassification bias may be either positive or negative and are consistent wi th random variation; there is little to suggest that bias is present in the studies analyzed. (C) 1999 Elsevier Science Inc.