Prevention Book

http://www.fpnotebook.com/

Lead-Time Bias

Aka: Lead-Time Bias, Leadtime Bias
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  1. See Also
    1. Screening Test
    2. Contingency Grid (includes Statistics Example)
    3. Test Sensitivity
    4. Test Specificity
    5. Negative Predictive Value
    6. Positive Predictive Value
    7. Likelihood Ratio
    8. Number Needed to Screen
    9. Length Bias
    10. Selection Bias
  2. Definition
    1. Early diagnosis falsely appears to prolong survival
  3. Example
    1. Disease 'A' is 100% fatal
    2. Disease 'A' lasts 7 years from onset to death
      1. Disease 'A' patients are asymptomatic for 4 years
      2. Disease 'A' median survival 3 years after diagnosis
    3. Screening Test can identify Disease 'A' early
      1. Detection occurs 2 years before clinical diagnosis
      2. Disease 'A' still lasts 7 years before death
        1. Disease 'A' is now asymptomatic for 2 years
        2. Disease 'A' median survival 5 years after diagnosis
    4. Screening Test falsely appears to prolong survival
      1. Screened and unscreened patients each survive 7 years
      2. Screened patients know diagnosis 2 years earlier
  4. References
    1. Gates (2001) Am Fam Physician 63(3):513-22
    2. MacLean (1996) Med Clin North Am 80(1):1-14
    3. Nielsen (1999) Med Clin North Am 83(6):1323-37

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