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What's Pretest probability?
probability of the disease before a test is done (basically the prevalence)

What's Posttest probability
 based on outcome of the test, the likelihood that the
 patient has the disease (rule in/out)

What's the table look like for Likelihood Ratios?

What's a positive likelihood ratio?
ration or proportion of those with disease & test positive: without disease with positive test result (1specificity)

What's the calculation for the positive likelihood ratio?

What's a Negative likelihood ration?
Ration = those with disease & negative test result : without disease and negative test result (specificity)

What's the equation for the negative likelihood ratio?

What are the components of framing a clinical question?
 P  patient/population being addressed
 I  intervention in question
 C  comparison (when relevant)
 O  outcome of outcomes of interest

What's the significance of LR >10 or <0.1?
 Generate large and conclusive changes from pretest and
 posttest probability.

What's the significance of LR of 510 and 0.10.2?
Generate moderate shifts in pretest to posttest probability.

What's the significance of LR of 25 and 0.50.2?
Generate small (but sometimes important) shifts from pre to posttest probability.

What's the significance of LR of 12 and 0.51?
Alter probability to a small (a likely insignificant) degree

What's a decision analysis?
Formal structure integrating evidence (beneficial/harmful effects) with values, preference, probablilitys, costs associated

What do squares, circles, and triangles represent on a decision analysis?
 Square decision
 Circle  chance events
 Triangle  outcome nodes

When are dignostic tests useful?
When there are large changes between pretest and posttest probability; validity compared to 'gold standard'

What factors affect predicitve valies the most?
prevalenceof disease, sensitivity, specificity

What are the advantages of LRs?
 Contribution of test result as a single number
 Determining post test probablilty given a result
 Summarizing information
 Describing probability of disease

What's the effect of having a low cutoff level on sensitivity/specificy?
Increase sensitivity

What's the effect of raising the cutoff level on specificity/sensitivity?
Increased sensitivity

