Factors that Affect Interpretation of Lab Data

Question 1

which anticoagulant is in purple top tubes?

Answer 1

EDTA

Question 2

which anticoagulant is in green top tubes?

Answer 2

heparin

Question 3

which anticoagulant is in blue top tubes?

Answer 3

citrate

Question 4

what are some properties of the sample that can lead to errors?

Answer 4

hemolysis
lipemia

Question 5

why are incompletely filled tubes a problem?

Answer 5

anticoagulant dilution factor
excess EDTA has osmotic effects

Question 6

what are some analytical sources of error?

Answer 6

expired reagents
failure to calibrate assay as needed
analyzer limitation
is method appropriate for species?

Question 7

what are some post-analytical sources of error?

Answer 7

transcription errors
results reported to wrong patient

Question 8

how many patients do you need to an ideal reference interval?

Answer 8

120 healthy patients

Question 9

reference interval reflects __________ of population

Answer 9

95%

Question 10

what is the diagnostic cut-off an alternative to?

Answer 10

reference interval: set an assay value as likely to be diagnostic for the disease of interest

Question 11

true/false: age and breed can affect reference values

Answer 11

true

Question 12

what are the assay diagnostic properties?

Answer 12

sensitivity
specificity
positive predictive value
negative predictive value

Question 13

what are the preanalytical errors?

Answer 13

poor collection technique
incorrect tube type
interfering substances
improperly labeled sample
damage during transport to lab

Question 14

what does EDTA do with calcium?

Answer 14

strongly chelates

Question 15

what does heparin do?

Answer 15

activates antithrombin

Question 16

does citrate chelate calcium?

Answer 16

weakly

Question 17

what are some errors in filling tubes?

Answer 17

sample forced through needle
incompletely filled
cross contamination between tubes

Question 18

what do calibrators and controls ensure?

Answer 18

reliability and consistency of assay results

Question 19

should each lab have its own reference intervals?

Answer 19

yes

Question 20

what do values of reference intervals depend on?

Answer 20

different reagents
cofactors
substrates
temperature

Question 21

are minor changes in comparison to reference intervals always significant?

Answer 21

depends on what looking at
no

Question 22

what does it mean for a test to be very sensitive?

Answer 22

good at testing for positives
few false negatives

Question 23

what does it mean for a test to be very specific?

Answer 23

good at testing for negatives
few false positives

Question 24

what are predictive values affected by?

Answer 24

sensitivity
specificity
disease prevalence

Question 25

is a highly specific or highly sensitive test a better screening test?

Answer 25

highly sensitive test

Question 26

which anticoagulants chelate calcium?

Answer 26

EDTA
citrate

Question 27

what is in a gray top tube?

Answer 27

potassium oxalate and sodium fluoridee

Question 28

what are some analytical sources of error?

Answer 28

expired reagents
failure to calibrate assay as needed
analyzer limitation
method appropriate for species?

Question 29

what do controls provide a means of evaluating?

Answer 29

assay’s consistency or reproducibility

Question 30

what ensure reliability and consistency of assay results?

Answer 30

calibrators and controls

Question 31

what are enzyme activities affected by?

Answer 31

amount of enzyme and sample age

Question 32

what increases on a chemistry with dehydration?

Answer 32

albumin
sodium chloride
PCV

Question 33

what does it mean that a test has 95% specificity?

Answer 33

95% true negatives
5% false positive rate

Question 34

what does it mean that a test has 95% sensitivity?

Answer 34

95% true positives
5% false negatives

Question 35

how do you calculate efficiency/accuracy?

Answer 35

(true positives + true negatives)/total patients

Question 36

increased specificity will increase the ____________________________ and decrease the ____________________________

Answer 36

positive predictive value
negative predictive value