QuestionSBA
QuestionChoice
Lead-time bias occurs when a disease is detected during a screening procedure while the patient is asymptomatic, and hence an earlier than usual diagnosis would be made for a given disease. Screening may only lengthen the time-period a person is considered a patient. This can be misinterpreted as an earlier diagnosis through asymptomatic screening causing an increased survival time.
10006782
b
Lead-time bias
QuestionChoice
Length-time bias occurs when patients with less severe disease are more likely to have those diseases detected through screening. Length-time bias leads to the incorrect assumption that screening was responsible for the higher survival rates, when in reality these results could have been caused by the difference in rates of disease progression. A rapidly-progressing disease will often present with severe symptoms which require immediate attention and are less likely to be detected through screening. These are also more likely to result in mortality. Slowly progressing diseases often remain asymptomatic for a period of time and are more likely to be detected by screening. These patients tend to have a longer survival period.
10006781
a
Length-time bias
QuestionChoice
Measurement bias is due to an error in data collection during measurement. No evidence of any measurement bias is shown here.
10006785
e
Measurement bias
QuestionChoice
Confirmation bias reflects the tendency to process information by specifically looking for information which is consistent with one's existing beliefs. This can often be unintentional, and may result in the ignoring of inconsistent information.
10006784
d
Confirmation bias
QuestionChoice
Selection bias occurs when the subjects in a study differ from the population of interest, resulting in an error of association or outcome. Ideally, the subjects in a study should be very similar to one another and to the larger population from which they are drawn. Insufficient information on the patient sample is provided here to determine whether selection bias is present.
10006783
c
Selection bias
Concept
Chapter
2693
3779
Breast Cancer
Topic
151
Breast Disease
13903
A study is performed on screening for breast cancer. The study states that screening patients for breast cancer resulted in a higher breast cancer survival rate. On closer analysis, the overall mortality rate was the same for screening and non-screening groups. However, those who were diagnosed through screening were generally found to have more slow-progressing forms of the disease.

Which of the following most appropriately describes the bias described in this study?
a