Diagnosis studies Flashcards
What are the answerable questions in EBM?
Patient
Intervention
Comparison
Outcome
What are the steps of EBM?
Ask questions Search for evidence Critically appraise Integrate Evaluate
When are diagnostic studies used?
Screen a population
Diagnose a pt
Pt f/u
What are the disadvantages of diagnosis studies?
May be expensive
Can risk morbidity/mortality
May cause discomfort
Are diagnosis studies randomized?
No
What are the four questions to ask when critically appraising diagnosis studies?
- What are the results
- Is the study valid
- Are results important
- Will results help my pt
What should always be included in diagnostic studies?
Comparison to the gold standard
What are the indications that a study is of clinical importance?
High sensitivity/specificity
The usefulness of any diagnostic test is based on what?
Its accuracy in identifying the disorder
What are likelihood ratios?
Predict the likelihood of a certain result in a pt WITH the target disorder, and one WITHOUT
True or false: likelihood ratios are essential in analysis of diagnostic studies
False-useful, but not essential
What is the equation for sensitivity?
True pos / True pos + false neg
What is the equation for specificity?
True neg / False pos + true neg
Does a specific test rule in or out?
rules in
Does a sensitive test rule in or out?
out
What is the incidence?
How many new cases occur in a given period of time
What is the prevalence?
How many cases are in a given population, old or new
What is the pretest probability?
all pos / all results (prevalence in a population)
What is the posttest probability?
Post-test odds/post test odds +1
A good test will do what to posttest probability?
Increase it significantly
What are odds?
with a condition / # without
How do you calculate odds knowing probability?
Probability / probability -1
What is a positive likelihood ratio?
sensitivity / 1-specificity
“the probability of a person who has the disease testing positive divided by the probability of a person who does not have the disease testing positive.”
What is a negative likelihood ratio?
1-sensitivity / specificity
“the probability of a person who has the disease testing negative divided by the probability of a person who does not have the disease testing negative”
