If rapidly progressive cancers are missed by a screening test, which type of bias will occur?
a. Rapidly progressive cancers will be less likely to be detected by a screening test if symptoms rapidly develop because the window period between the time the cancer can be detected when it is asymptomatic by a screening test and the time it will become clinically apparent is short. This is described as length bias. Screening tests will yield better outcomes because they detect more slowly growing tumors.
b. Lead-time biasoccurs when the screening test advances the time of diagnosis, but no true prolongation of life occurs because survival for women who are screened and those who are not is the same from the time the cancer occurs. Information bias occurs when there is a systematic difference in the way data are collected (inaccurate or imprecise measure) for either the exposure or the outcome.
c. Recall bias is one form of information bias.
d. Selection biasoccurs when the inclusion of a subject in a study group is linked to the exposure of interest. As an example for a case-control study, if women who use oral contraceptives are suspected more often of having deep vein thrombosis (DVT), they would be hospitalized more often for evaluation and diagnosed more often than controls.
e. Selection bias can also occur in cohort studies and is related to differential loss to follow-up. Surveillance bias refers to overdetection of the disease of interest because one of the groups goes to the doctor (or has a diagnostic test) more often than does another group. For example, women who take postmenopausal estrogens presumably go to the doctor (and probably have mammograms) more frequently than women who do not; thus, women who take estrogens may be more likely to have breast cancers detected because of the increased surveillance.