Applying epidemiologic and biostatistical reasoning to patient management decisions as tested on USMLE Step 3.
About this set
35 basic cards for USMLE Step 3 Internal Medicine. It opens with "As disease prevalence decreases in a population, what happens to a screening" and "As disease prevalence decreases in a population, what happens to a screening". More Healthcare and Nursing decks are listed below.
35 cards · basic cards · AI-written, checked twice. Edit anything.
- As disease prevalence decreases in a population, what happens to a screening test's positive predictive value (PPV), assuming sensitivity and specificity stay constant?
Show answer
PPV decreases.- As disease prevalence decreases in a population, what happens to a screening test's negative predictive value (NPV), assuming sensitivity and specificity stay constant?
Show answer
NPV increases.- Do a test's sensitivity and specificity change as disease prevalence in the tested population changes?
Show answer
No, sensitivity and specificity are intrinsic properties of the test itself and do not change with prevalence.- A highly sensitive test is best used for what clinical purpose?
Show answer
Ruling out disease, since a negative result argues strongly against having the disease.- A highly specific test is best used for what clinical purpose?
Show answer
Ruling in disease, since a positive result argues strongly for having the disease.- How is sensitivity calculated?
Show answer
True positives divided by (true positives plus false negatives).- How is specificity calculated?
Show answer
True negatives divided by (true negatives plus false positives).- How is positive predictive value (PPV) calculated?
Show answer
True positives divided by (true positives plus false positives).- How is negative predictive value (NPV) calculated?
Show answer
True negatives divided by (true negatives plus false negatives).- What does a positive likelihood ratio (LR+) greater than 10 indicate about a positive test result?
Show answer
It substantially raises the probability that the patient has the disease.- What does a negative likelihood ratio (LR-) close to 0 indicate about a negative test result?
Show answer
It substantially lowers the probability that the patient has the disease.- How is the positive likelihood ratio (LR+) calculated?
Show answer
Sensitivity divided by (1 minus specificity).- In Bayesian clinical reasoning, ____ combined with a test's likelihood ratio determines the posttest probability of disease.
Show answer
pretest probability- What does number needed to treat (NNT) represent?
Show answer
The number of patients who must be treated to prevent one additional bad outcome.- How is number needed to treat (NNT) calculated?
Show answer
1 divided by the absolute risk reduction.
FlashKeepers