Introduction</h5> Rarely if ever do studies of risk factors for chronic disease take into account bias from screening, even though many behavioral risk factors may be associated with use of screening. Weiss  and Joffe  describe some ways in which screening modifies the observed risk-factor-disease associations and complicates interpretation of results. Lead time, the interval by which disease diagnosis is advanced by screening [3–9] , has rarely been recognized to bias such comparisons of incidence or mortality  , and when it has, it has been approached heuristically rather than analytically  . Differential ascertainment can occur within a study between subjects who are screened routinely and their counterparts who are not, regardless of screening efficacy. Because the factors that drive the differential ascertainment act before the data collection period, conventional methods for confounding adjustment cannot adequately address such selection bias. For these reasons, lead time–biased case ascertainment (LTBCA) may be more widespread than generally recognized and also problematic to control, thus motivating new methods.</P>This bias can affect any observational study type, including a cohort study in which a disease risk factor is also associated with screening, for example, a study of physical activity and prostate cancer
Annals of Epidemiology – Elsevier
Published: Nov 1, 2013
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