Screening Flashcards
What is sensitivity?
how well a test can detect presence of disease when a disease is present. It also the proportion of TIME that a test is positive in a patient that does have aidease.
How is sensitivity calculated?
TP/(TP+FN) x 100 or TP/(all diseased) x 100
What is specificity?
How well a test can detect the ABSENCE of disease when the disease is absent. It is also the proportion of time that a test is negative in a patient that does not have the edisease.
How is specificity calculated?
TN/(TN+FP) x 100% or TN/(all not idseased) x 100
What do specificity and sensitivity have in common?
neither terms are predictive in an individual patient (properties of the test)
What is the positive predictive value (PPV)?
how accurately a positive test predicts the presence of disease. It is the percentage of TP’s in patients with a positive test (correct prediction).
How is PPV calculated?
TP/(TP+FP) x 100% or TP/(all positive tests) x 100%
`What is negative predictive value (NPV)?
how accurately a negative test predicts the absence of disease.. It is the percentage of TN’s in patients with a negative test (correct prediction).
How is NPV calculated?
TN/(TN+FN) x 100% or TN/(all negative tests) x 100
What is diagnostic accuracy/diagnositic precision?
Proportion of time that a patient is correctly lidentified as either having a disease or not having a diasease with a positive or negative test, respectivetly.
How is diagnostic accuracy/diagnostic precision calculated?
DA/DP = (TP + TN) / (TP+FP+FN+TN) x 100 or TP+TN/(all patients) x 100%
What are likelihood ratios?
Ratio of the probability of a given test result for a presron with the disease divided by the probability of the same test result without the disease. It can be caulculated fro both positive and negative test results.
What is the likelihood ratio positive?
probability of a positive test in either the presence or absence of a disease.
How is the likelihood ratio positive calculated?
A/(A+C) / B/(B+D)
What is the likelihood ratio negative?
the probaiblity of a negative test in the presence or absence of disease.
How is likelihood ratio negative calculated?
C/(A+C) / D/(B+D)
In order for a test to be beneficial, what should the value of LR+ be?
> 10
In order for a test to be beneficial, what should the value of LR- be?
What is the receiver operator curve?
A curve that shows the relationship between sensitivity and specificity for tests with numerical continous outcomes.
What is validity?
Ability to accurately discern between those that do and thosse that do not have the disease; e.g. telling the truth.
what is internal validity?
extent to which results accurately reflect what was being assessed (true situation of the study population().
What is external validity?
extent to which the results are applicable to to the populations (not included in the original study, also known as generalizibility).
What is reliability?
ability of a test to give the same result on repeated uses. A test may be reliable, but not always valid (e.g. you can always hit the outside of the ring when playing darts, but it is not valid because you are not hitting the center).
