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

Which of the following biases involves the loss of subjects affecting follow-up results?

1. Follow-up bias

2. Recall bias

3. Information bias

4. Ascertainment bias

The correct answer is: Follow-up bias

Follow-up bias occurs when the individuals who are lost to follow-up differ significantly from those who remain in the study, potentially skewing the results. This bias can lead to inaccurate conclusions if the reasons for loss to follow-up are related to the outcome of interest. For instance, if sicker patients drop out of a study, the remaining participants may not accurately represent the original population, thus invalidating the findings. This concept highlights the importance of maintaining participant engagement throughout the study to ensure that the results are representative of the intended population. Other types of biases, such as recall bias or information bias, involve different dynamics related to how data is collected or remembered, rather than the impact of losing participants over time. Ascertainment bias pertains to the method by which participants are identified or selected, which also differs from the specific issue of follow-up loss affecting results.