Lecture 1 Flashcards
what 3 things affect the quality of laboratory results?
Quality of sample (pre-analytic)
Quality of analysis (analytic)
Quality of lab and patient records (post-analytic)
In what phase does most errors in human medicine occur?
Pre-analytic phase
What technical factors can affect pre-analytic errors?
Test selection
Sample tube and fill (make sure using proper tube and fill it to specific line indicated, also make sure tubes are in date)
Sample collection ( use proper needle size etc.)
Sample identification
Sample handling and delayed processing
What Physiologic factor affects pre-analytic errors?
Patient preparation
What is the difference between serum and plasma chemistry?
Serum chemistries are allowed to clot (clotting factors have been removed)
Plasma chemistries contain clotting factors (proteins) in the tube that interact with the sample and keep it from clotting
What tubes are used for whole blood/plasma?
Ex: complete blood count
EDTA tube (purple top)
What tubes are used for plasma chemistry?
Ex: plasma chemistry, ammonia
Lithium heparin (green top)
Can green top tubes be used for CBC?
yes
What tubes are used for coagulation testing?
Citrate (blue top)
What tube is used for most biochemical tests?
Serum (with and without separator)
What sample is submitted for chemistry panels, serology, vitamin E, and most endocrinology tests except for endogenous and insulin ACTH?
Red top labeled serum
What sample is submitted for for ACTH endogenous & ACTH and insulin?
EDTA labeled plasma
What sample is submitted for hemograms, PCR tests, lead, selenium, and knott’s heartworm and BVDV PI testing in calves?
EDTA labeled whole blood
Do you centrifuge EDTA whole blood samples?
NO!
What sample is for toxicology testing of copper, iron, nitrate/nitrite, zinc, and pre- purchase drug screens?
Can also be used for most clin path chemistry tests
Green top labeled heparinized plasma
What is submitted for Knott’s heartworm and many toxicology tests including selenium and lead?
Green top labeled Heparin whole blood
What sample is submitted for most comparative coagulation tests?
Blue top labeled citrate plasma
Serum vs. plasma?
Potassium, LDH, P
Serum>plasma
Serum vs. plasma
AST, CK in cattle/sheep
Serum>plasma
Serum vs. Plasma
total proteins, globulins
Plasma>serum
What sample tube would you choose if you needed an anticoagulant selection?
Lithium Heparin (green top)
What can happen to serum tube blood with EDTA contamination?
Increased potassium/ decreased Ca 2+ and Mg 2+
Decreased bicarbonate, ALP, CK, glucose, amylase and lipase can also be decreased
What order of tubes do you place blood in to prevent EDTA contamination?
serum tube first then EDTA tube
How do dextrose containing fluids affect blood samples?
Low sodium, potassium, chloride from fluid dilution
high glucose from dextrose
What important factors should be remembered when handling and shipping sample?
Samples should be kept cool to minimize cell changes but wrapped in paper towels to prevent freezing and lysis of RBC and WBC
Blood smears should be made from freshly collected blood and submitted with tubes to facilitate blood smear exam and ensure accurate results
What are some pre-analytic problems that can occur with old blood samples?
Cell lysis, Erythrocyte swelling, and platelet activation
What are some other pre analytic factors that can occur with aged samples
Platelet, leukocyte, and erythrocyte clumps
Clot formation
What pre-analytic problems can occur with prolonged storage of samples?
Decreased glucose because glycolysis continues in the cells even after collection
Increased K+ because it leaks from the erythrocytes in K+ rich RBC’s
What animals have potassium rich RBC’s
Horses, Japanese dog breeds, camelids, pigs, sheep, and some cattle
What pre- analytic factors can affect the sample during storage?
Exposure to light
Evaporation (when sample left uncovered)
Freezing
What occurs when the sample is exposed to light?
Bilirubin is degraded
What occurs when the sample is left uncovered and undergoes evaporation?
Electrolytes are falsely increased because there is less water so more concentrated
What occurs when the sample gets frozen?
Falsely increased electrolytes due to the sublimation of water
What can occur in the sample if the patient is not properly fasted before collection?
Lipemia
What are some analytic factors that can affect the results from the sample?
Test performance Quality control (how good lab actually is) Results review Equipment limitations Calibration inaccuracies
What can you do to improve quality control?
Examine stained blood films!
What do you want to do if you have thrombocytopenia or leukopenia in your test results?
Check a blood stained smear to look for cell clumping
In what species, is cellular clumping very common?
CATS!
What are sometimes counted as leukocytes in manual and automated cell counters?
Nucleated RBC’s
IN what disease states are nucleated RBC’s common ?
Regenerative anemia
Lead toxicity
Marrow injury or disease
Other inflammatory diseases
True/ False:
If more than 5 nucleated RBC’s are counted per 100 WBC then the WBC count will need to corrected
True
What is the formula for a corrected WBC count?
(Measured WBC count X 100) / (100 + nucleated RBC)
2 ways to differentiate a nucleated RBC from a lymphocyte
Nucleated RBC’s have:
complete rim of cytoplasm
more eosinophilic cytoplasm
What are the primary biochemical methodologies?
Photometry and Electrochemistry
what is spectrophotometry used for?
Wet chemistry to measure the absorbance of light
A=cal (Beer’s law
How is dry chemistry evaluated?
Reflectance (see how much light is reflected back)
what are some matrix issues that affect the analysis of the blood sample?
Lipemia icterus Hemolysis Hyperproteinemia Drugs
Looks like tomato juice interferes with spectrophotometric assays? due to lysis of RBC’s
Hemolysis
Occurs when animals have not been properly fasted before blood collection or with hyperlipidemic syndromes?
Lipemia
Can dilute out normal substances like K+, Na+, Cl- in the aqueous component and causes decreased concentration of these (ion exclusion effect)
Lipemia
What is the ion exclusion effect?
analyzer measures electrolytes by adding H20 to the sample –> lipemia displaces amount of H20 added to the sample so analyzer measures from a smaller fraction resulting in fewer electrolytes being measured
Looks like orange juice due to increased bilrubin in sample
Icterus
There is a 5% chance you will get an abnormal test result in a healthy animal when measuring ______ value
1
There is a 64% chance you will get an abnormal test result in a healthy animal when measuring _____ values
20
