Biostatistics & Study Design USMLE Step 1 Practice Question
A hospital initiates annual low-dose CT screening for high-risk smokers (age 55-75, ≥30 pack-years). Five years later, screened patients (BP 138/82, HR 78, RR 16, SpO2 98%) demonstrate increased median survival post-diagnosis compared to unscreened controls, yet disease-specific mortality remains identical between groups. CT findings show early-stage nodules in screened cohort. Notably, no difference exists in overall mortality. Which phenomenon best explains the improved survival interval without mortality benefit?
Answer choices
- ALead-time biasCorrect answer
- BLength-time bias
- CRecall bias
- DSelection bias
- EConfounding by indication
- FHawthorne effect
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