Misclassification of exposures such as sex partners, paid sex and STI may be present in all studies based on self-reported risk factors.
First, categorization of continuous variables can result in misclassification of exposures such as the MetS components and CRP.
Although nutritional data collected 10 years earlier may have resulted in some misclassification of exposure, such misclassification is likely to be nondifferential in relation to knee structure, since only subjects with no history of knee symptoms or injury were included.
Misclassification of injuries (such as a faulty diagnosis of acute lateral ankle ligament sprains) sustained during the follow-up, however, was possible.
However, data from death certificates have several limitations, including the possible coding of inaccurate information through careless completion of cause of death, coding errors, and misclassification of variables such as race/ethnicity (25, 26 ).
While nutritional data collected 10 years earlier may have resulted in some misclassification of exposure, such misclassification is likely to have been non-differential in relation to knee structure since only subjects with no history of knee symptoms or injury were included, thereby tending to underestimate the strength of any observed associations.
Because Cd has a long half-life in the kidney, the use of only the current residential address in the exposure estimate is likely to lead to random misclassification of exposure, such that any relationship between modeled air Cd concentrations/distance from smelter and U-Cd would be biased toward the null.
Third, differential misclassification of covariates such as type 2 diabetes is possible because type 2 diabetes was only excluded in the control patients but not in the CD patients by 75-g oral glucose tolerance tests due to the necessary fluid restriction in the latter group.
