Diagnostic value of tests

Question 1

Minimum laboratory data base

Answer 1

CBC, Chem, UA

used for: wellness checks and pre-op screening, dx, px, monitoring

Question 2

factors that influence the diagnostic value of laboratory tests

Answer 2

pre-analytical-influence results prior to sample analysis

analytical: influence the process of testing

post-analytical: influence interpretation

Question 3

pre-analytical error

Answer 3

Patient and sample variables

age, breed, diet, excitement

drugs

lipemia, hemolysis, icterus

sample labeling

collection, processing and storage

Question 4

lipemia

Answer 4

lactescence from lipids

food consumption or metabolic disease

Question 5

hemolysis

Answer 5

hemoglobin in serum/plasma

in vitro or in vivo

Question 6

icterus

Answer 6

increased bilirubin

Question 7

collection

Answer 7

correct tube

fill tube properly-dilutional effects

mix blood with anti-coagulant immediately and gently

Question 8

process and storage

Answer 8

CBC: mix, fill hematocrit tube and make smear, DON’T freeze, no formalin exposure

Serum: allow to clot, spin immediately, refrigerate to store

urine: note source, analyze within 30 mins or refrigerate, bring to RT before analysis

Question 9

accuracy

Answer 9

agreement between result and “true value”

Question 10

precision

Answer 10

agreement between replicate measures or “repeatability”

Question 11

validation

Answer 11

compare new method with reference method or “gold standard”-accuracy

evaluate precision

linearity, detection limits and interferences

normal and diseased animals

very important when “exporting” tests from one spp to another

Question 12

Construction of reference intervals: selection of individuals

Answer 12

40-120 animals that reflect your patient population

Healthy animals with no meds except parasite control

factors that impact intervals: genetic background/breed, sex & repro status, diet & other husbandry conditions, age

Question 13

construction of reference intervals: impact of analytical methodology

Answer 13

RI specific to the way the test was performed

impacted by kind of machine, reagents, etc

hematology RI less impacted by methodology than chemistry RI

Question 14

Reference interval construction

Answer 14

mean +/- 2 SD OR the central 95% of animals

5% of normal patients will be outside RI

Question 15

Reference interval construction: interpretive implications

Answer 15

reference intervals does not equal normal values

normal patients can have values outside of RI and 5% do

sick patients may have values within RI

Question 16

Analytical error: quality assurance

Answer 16

SOP: step by step instructions for performing testing

Calibration: adjustment of instrument to known standard

controls: test performance of system using materials of known values