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
Prevalence. definition?
Measure of the TOTAL number of cases (new and old) measured at a particular point in time
Incidence. 2 points to remember?
- Measuring incidence:
a. Make sure you define the TIME PERIOD during which new cases is counted
b. Make sure you include only the population at risk of acquiring the disease
prevalence incr –> PPV?
incr
prevalence decr –> PPV?
decr
prevalence incr –> NPV?
decr
prevalence decr –> NPV?
incr
Precision (reliability)? patikimumas. definition?
The consistency and reproducibility of a test.
Absence of random variation in a test
Accuracy (validity)? pagrįstumas. definition?
the trueness of test measurement.
The absence of systematic erroc or bias in test.
It means how much the test results agree with the gold standard test.
