Diagnostic test/prev/incid Flashcards
Sensitivity definition?
the probability of a diseased person testing positive
Specificity definition?
the probability of a non-diseased person testing negative
PPV definition?
the probability that person who has a positive test, actually has the disease
NPV definition?
the probability that person who has a negative test, actually does not have the disease
Positive likelihood ratio definition?
a ratio representing the likelihood of having the disease given a positive result
Negative likelihood ratio definition?
a ratio representing the likelihood of having the disease given a negative result
sensitivity formula?
TP/ (TP+FN)
specificity formula?
TN/ (TN+FP)
PPV formula?
TP/ (TP+FP)
NPV formula?
TN/ (TN+FN)
+LR formula?
Sensitivity/ (1-specificity)
-LR formula?
(1-sensitivity)/ specificity
Sensitive tests have many ….
FP
Specific tests have few ….
FP
SN-N-OUT?
sensitive tests, if negative, rule out the disease
SP-P-IN?
specific tests, if positive, rule in the disease
sensitivity. value approaching 100 proc. is desirable for ruling OUT DISEASE and indicates a low FN rate
.
specificity. value approaching 100 proc. is desirable for ruling IN DISEASE and indicates a low FP rate
What test for screening?
sensitivity
what test used for confirmation after a positive screening test?
specificity
increasing prevalence of disease increases ……
PPV
PPV varies directly to prevalence
decreasing prevalence of disease increases ……
NPV
NPV varies inversely to prevalence
LR +/- ranges?
LR+ > 10 and/or LR- <0,1 indicate a very usedul diagnostic test
Incidence. definition?
Measure of NEW cases that develop in a population over a certain period of time