step II

  1. Sensitivity
    • finds disease used to screen
    • Excludes disease if test negative, Includes disease is test is positive
    • TP/TP+FN
  2. Specificity
    • How good in normal population
    • used to confirm disease
    • TN/TN+FP
  3. Reference interval
    +/- 2SD = 95% of normal
  4. Negative Predictive Value
    • How likely the negative result is a true negative and not a false negative
    • - with a 100% sensitive test = 100% b/c there are no false negatives
    • -with a 100% specific test = could be TN or FN does not exclude disease
    • -TN/TN+FN
  5. Highly sensitive test
    ...increases prevalance of disease
  6. Increasing upper limit of normal of a test reference interval
    • increases specificity and PPV
    • decreases sensitivity and NPV
  7. decreasing upper limit of normal on test reference interval
    • increases sensitivity and NPV
    • decreases specificity and PPV
  8. Prevelance
    • Prevelance = incidence x duration
    • TP+FN/ TP+FN+TN+FP

    • -prevelance is how many people have the disease right now. It increases as the duration of a disease increases.
    • -incidence is how many people develop a disease in a population over a set time, usually one year.
  9. Positive predictive value
    • how likely a positive result is a true positive
    • -TP/TP+FP
    • -100% sensitive test = result could be TP or FP includes people with disease but does not confirm
    • -100% specificity = 100% b/c there is no false positives, confirms disease!
Card Set
step II
HY fact review