Epidemiology & Prevention USMLE Step 1 Practice Question
A 62-year-old man with 45 pack-year smoking history presents for routine follow-up. CT chest screening reveals a 1.2-cm nodule (Lung-RADS 3); PET-CT shows no hypermetabolic activity. Five years post-diagnosis, screened patients demonstrate significantly longer overall survival compared to unscreened controls, yet lung cancer-specific mortality rates remain identical between groups. He denies hemoptysis and maintains baseline functional status. Which phenomenon best explains the improved survival difference despite unchanged disease mortality?
Answer choices
- ALength-time bias
- BRecall bias
- CSelection bias
- DLead-time biasCorrect answer
- EConfounding by indication
- FImmortal time bias
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.