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

What type of bias may occur if early detection of disease causes a perception of increased survival?

1. Lead time bias

2. Recall bias

3. Ascertainment bias

4. Odds Ratio bias

The correct answer is: Lead time bias

Lead time bias occurs when earlier diagnosis of a disease results in a longer period during which a person is known to have the disease, thus creating the illusion of increased survival time. This phenomenon can make it appear as though patients who are diagnosed earlier live longer after their diagnosis than those diagnosed later, even though the actual time to death may not differ. By detecting the disease sooner, the time between diagnosis and death is lengthened merely due to the earlier detection—not because of an improvement in the actual course of the disease or effectiveness of treatment. In contrast, recall bias refers to differences in the accuracy or completeness of recollections retrieved by study participants regarding past events, which does not apply in this context. Ascertainment bias involves systemic differences in how subjects are selected or how data is collected, usually impacting study results. Odds Ratio bias refers to discrepancies associated with estimating the odds of an outcome, often seen in case-control studies. While these other types of bias are relevant in different contexts, lead time bias specifically addresses the scenario presented in the question, making it the correct choice.