Epidemiology & Prevention USMLE Step 1 Practice Question
A 58-year-old woman undergoes mammography screening and is found to have a 1.2-cm breast mass with negative axillary lymph nodes on imaging. Her vital signs are stable (BP 128/82, HR 72, RR 14, Temp 98.6°F, SpO2 98%). However, another woman in the same program develops symptomatic breast cancer between screening intervals with metastatic disease at diagnosis. Which bias best explains why screened tumors appear to have more favorable 10-year survival rates despite similar underlying disease biology?
Answer choices
- ABerkson bias
- BLength-time biasCorrect answer
- CObserver-expectancy bias
- DAttrition bias
- EMeasurement bias
- FLead-time bias
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