wk 8 - diagnostics Flashcards
diagnostic accuracy study tells you what
value of a diagnostic test
% of ruling in and ruling out condition
diagnostic utility study tells us what
overall usefulness of a test considering the impact on patient outcomes and decision making
screening tests are used to
test asymptomatic people to identify those at increased risk of a condition.
good for early detection and prevention
diagnostic tests are used to
determine presence or absence of a condition for people who are symptomatic or tested positive in screening test.
clinical decision tools are used to
assist in making decisions around patient care
ottawa ankle rules
harms of diagnostic testing
time
cost
pain
radiation
incorrect diagnosis
diagnostic study PICO
population
index test
comparator test
outcome
measures for diagnostic tests
accuracy
sensitivity
specificity
postivite predictive value
negative predictive value
positive likelihood ratio
negative “
true positives
people that do have the condiiton, test having the condition
true negative
poeple that dont have the condition, test negative to having condition
false positive
people that dont have the condition, test having the condition
false negative
people that have the condition, test negative to having the condition
accuracy refers to what, whats the formula
what proportion of all tests have given the correct result
true positive plus true negative number of results / 100 to give a percentage
16 plus 60 /100 equals 76% accuracy
accuracy can be misleading when
conditions are rare or there are large differences in numbers with people that have it or dont have the condition according to the reference test
sensitivity
number of people with the disease that have a positive test
high sensitivity for a test and a negative result
rule out condition
forumla for sensitivity
true positive / everyone that has the condition according to reference test equals percentage
specificity
people without the disease that test negative
high specificity in a test and positive test
rule in condition
formula for specificity
true negative/ total of people who dont have the condition according to reference test equals percentage
positive predictive value
people with a positive test who have the condition
negative predictive value
people with a negative test who dont have the condition
positive likelihood ratio
how much more likely is a positive test to be found in a person with the codnition than a person without it
negative likelihood ratio
how much more likely is a negative test to be found in a person without the condition than a person with it
ROC curve
helps understand specificity (confirming disease) and sensitivity (screening disease)
what critical appraisal tool for diagnostic studies
SIGN checklist
