Diagnostic studies

Question 1

are diagnostic studies randomized?

Answer 1

no

Question 2

definition: sensitivity

Answer 2

how well a test finds people WITH the condition

proportion WITH the disease testing positive

SnNout - if test has high sensitivity and is negative, the condition is ruled OUT

Question 3

definition: specificity

Answer 3

how well a test finds people WITHOUT the condition

proportion WITHOUT the disease testing negative

SpPin - if test with high specificity is positive, rules the condition IN

Question 4

definition: likelihood ratio

Answer 4

predicts likelihood of a certain result in a patient WITH the target disorder when compared to the likelihood of the same result in someone WITHOUT it

Question 5

definition: pre test probability

Answer 5

1. based on estimates of prevalence (how often a condition is found in the public)
2. commonly based on long term experience or diseases in specific populations
3. calculated as “all pos / all results”

Question 6

what does a likelihood ratio greater than 1 mean?

Answer 6

test has increased probability that you have found the disorder of interest

Question 7

what does a likelihood ratio less than 1 mean?

Answer 7

test has decreased probability that you have found the disorder of interest - NOT A USEFUL TEST

Question 8

what does a likelihood ratio = 1 mean?

Answer 8

test is useless - pretest probability = posttest probability

Question 9

definition: Bayes’ theorem

Answer 9

likelihood of a particular condition being present in an individual is directly proportional to the prevalence of that condition in the population

prevalence in the population determines how likely you are to rule in/out a test