
What is the minimum # of subjects required to establish a reference interval? (according to this text)
60

Reference limits for data showing a normal distribution are calculated values representing what?
Mean+/ 2 SD

What is the likelihood of one value falling outside the Ref. Int?
(10.95n)x100

T/F: Reference intervals represent results expected in all healthy animals.
F represents expected results in 95% of healthy animals

"Why is ""reference range"" and inappropriate term?"
b/c statistically it means the difference b/w the high and low values

T/F: Analytical precision is the ability of an assay to get the same result if the same sample is analyzed several times
T

"Calculate the CV for the following diagnostic tests. Test A: Mean=10, SD=3, Test B: Mean=50, SD=4"
"A:30%, B:8%" CV=(SD/Mean)x100

Which test is more precise?
B low CV> high prec

T/F: Withinassay CV represents random error w/in a run of the assay and the error from additional runs of the assay on the same sample.
F That is betweenassay CV

"If a clinical decision is based on a minimal change in the value of an analyte, should the CV be high or low?"
Low

What term represents the ability of a test to produce a change in the signal for a defined change of the quantity?
Analytical Sensitivity

Define accuracy.
the closeness of the agreement b/w the measured value and the true value

Define analytical specificity
ability to detect only the substance of interest freedom from interference

T/F: A test w/ high diagnostic specificity is a good screening test.
"F, screening tests should have high sensitivity"

A test w/ high diagnostic sensitivity has few (FN/FP) results. Choose one
FN

Define positive predictive value.
the probablitiy that a positive test indicates that the animal has the disease PPV=TP/(TP + FP)

"When prevalence is low, which is more likely to occur? FN or FP"
FP

A test with few FN compared to TN results has a high (PPV/NPV). Choose one.
NPV NPV=TN/(TN +FN)

T/F: The clinical value of the calculated diagnostic properties is influenced by prevalence.
T

PPV is less when the disease prevalence is (high/low). Choose
low

"Disease prevalence=10%, n=1000, sensitivity=94%, specificity=85%. Calculate TP, FP, TN, FN, PPV and NPV"
"TP=94, FP=135, TN=765, FN=6, PPV=41%, NPV=99%"

What happens to the PPV when the prevalence increases to 25%?
It increases b/c TP increase and FP decrease

