Lab Tests

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Lab Tests
2010-11-06 22:16:23
Lab Tests

Lab Tests
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  1. Can calculate the revised probability (RP) from the initial probability (IP) of the diagnosis by knowing what 3 things? What is this called?
    • The prior probability of the disease
    • The probability of a positive test result with the disease
    • The probability of a positive test result without the disease
    • Called Bayes' Theorem
  2. Good as screening test in disease with low prevalence; low false-negative (FN) rate; e.g. cancer screening tests, PSA, ELISA, HIV, etc.
    High Sensitivity
  3. A test with a low false-positive (FP) rate; good for confirming a positive obtained on a screening test; e.g. a positive ELISA HIV test must then be confirmed with a Western Blot assay
    High Specificity
  4. The percentage of patients with a "positive" result from a population with the disease (TPR)
    Sensitivity of True Positive Rate (TPR)
  5. The percentage of people with a "negative" test in a population without the disease (TNR)
    Specificity of True Negative Rate (TNR)
  6. False positive rate = ?
    FPR = 1 - specificity
  7. False negative rate = ?
    FNR = 1 - sensitivity
  8. SNOUT
    • SeNsitivity "N" test rules out or Sn-N-Out disease:
    • High sensitivity + Negative result --> Rules out diagnosis
  9. SPIN
    • SPecificity "P" rules IN or Sp-P-IN disease:
    • High specificity + Positive result --> Rules in diagnosis
  10. The ratio of the probability of finding a positive test in the presence of disease to the probability of a positive test in the absense of disease
    Likelihood Ratio