American Board of Surgery Qualifying Exam (ABS QE) Practice Test

What does follow-up bias imply in a study?

1. A difference in follow-up related to the exposure

2. A tendency to give socially approved answers

3. Bias introduced by earlier disease detection

4. Distortion due to factors affecting both exposure and outcome

The correct answer is: A difference in follow-up related to the exposure

Follow-up bias in a study refers to the situation where the rates of follow-up differ based on the exposure status of the participants. This bias can occur if individuals who were exposed are more or less likely to adhere to follow-up appointments than those who were not exposed. This discrepancy can skew the results, leading to inaccurate conclusions about the effects of the exposure on the outcome being studied. For example, if patients who received a certain treatment are also more likely to drop out of follow-up assessments, the study may inadvertently suggest that the treatment is less effective or more harmful than it actually is, simply because the follow-up data is not representative of all patients. The other choices address different types of biases that can occur in studies: social desirability bias in relation to how people respond to surveys, lead time bias concerning the detection of diseases, and confounding bias where external factors influence both exposure and outcome. While these are all important concepts, they do not specifically capture the essence of follow-up bias.