Prevention Book


Lead-Time Bias

Aka: Lead-Time Bias, Leadtime Bias
  1. See Also
    1. Screening Test
    2. Contingency Grid or Cross Tab (includes Statistics Example)
    3. Bayes Theorem (Bayesian Statistics)
    4. Fagan Nomogram
    5. Experimental Error (Experimental Bias)
    6. Length Bias
    7. Selection Bias
    8. Likelihood Ratio (Positive Likelihood Ratio, Negative Likelihood Ratio)
    9. Number Needed to Screen (Number Needed to Treat, Absolute Risk Reduction, Relative Risk Reduction)
    10. Negative Predictive Value
    11. Positive Predictive Value
    12. Pre-Test Odds or Post-Test Odds
    13. Receiver Operating Characteristic
    14. Test Sensitivity (False Negative Rate)
    15. Test Specificity (False Positive Rate)
    16. U.S. Preventive Services Task Force Recommendations
  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 [PubMed]
    2. MacLean (1996) Med Clin North Am 80(1):1-14 [PubMed]
    3. Nielsen (1999) Med Clin North Am 83(6):1323-37 [PubMed]

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