DIAGNOSTIC TEST PERFORMANCE Flashcards
what is the sensitivity of a test?
measures how often a test correctly generates a positive result for people who have the condition that’s being tested for - the true positives
what is the specificity of a test?
the proportion of people WITHOUT Disease X that have a NEGATIVE blood test.
what is misclassification bias?
when individuals are assigned to a different category than the one they should be in
what is a gold standard test?
the best available diagnostic test that determines whether a patient does or doesnt have a disease
what are true positives and true negatives?
TP- has the disease and tests positive
TN- hasn’t got disease and tests negative
what are false positives and false negatives?
FP- hasn’t got disease but tests positive
FN- has disease but tests negative
how do you know if a test is good?
if the gold standard test results = your test results
how do you work out sensitivity?
true positive results / all with disease
how do you work of specificity of a test?
true negatives / all without disease
how do you work out the positive predicted value?
true positives / test positives
how do you work out the negative predictive value?
true negatives / test negatives
how do you work out the likelihood ratio of positive test results?
sensitivity / 100-specificity
how do you work out the likelihood ratio of a negative result?
100-sensitivity / specificity
what does a large likelihood ratio of a positive result mean?
the greater the chance of having the disease if the test is positive
what is a positive predictive value?
the probability that subjects with a positive test truly have the disease
