Lecture 1 - Introduction to CP Flashcards
What 3 general things determine the quality of laboratory results
- preanalytic factors (sample quality) - patietn prep, collection tech, container, volume, handling, labeling
- Analytic factors (analysis quality) - method, quality of equipment, quality control
- post analytic factors (lab and patient record quality) - Min transcriptional errors, data presentation
What area do 90% of mistakes occur regarding lab tests
preanalytic! mostly technical issues not patient issue
usually issues with patient prep, sample collection, container used, volume given, how sample is handled, and improper labeling
__ phase involves all steps from test selection and sample collection to analysis.
pre-analytic, most errors occur here!
What are 5 technical/non-biological factors that occur in the pre-analytic phase can cause error
- test selection
- sample tube and fill
- sample collection
- sample ID
- sample handling and delayed processing
“HIT SC”
What physicological/biological factor is in the pre-analytic phase that can be means for an error
- patient preparation
__ can clot bc clotting factors are removed where the __ will not clot bc there are clotting factors present in it.
serum, plasma
clotting factors are proteins
purple top tube (chemical, sample, test)
chemical: EDTA
Sample: whole blood or plasma (has clotting factors)
test: CBC
green top tube (chemical, sample, test)
chemical: lithium heparin
sample: whole blood or plasma (has clotting factors)
test: plasma chemistry, ammonia, CBC
blue top tube (chemical, sample, test)
chemical: citrate
sample: whole blood or plasma (has clotting factors)
test: coagulation testing
serum tubes (with (tiger top) or without (red top) separator) used for
biochemical tests and most endocrinology tests
most labs reference samples are based on __
serum samples
The most common mistake is ___ contamination when putting samples into tubes
EDTA
With EDTA contamination __ will be artifactually increased to suprephysiologic levels
potassium
EDTA contamination artifactually decreases __ and __
Ca and Mg
EDTA ___ causing a decrease in Ca and Mg
chelates divalent cations
EDTA contamination effects which enzyme reactions that use Ca and Mg causing decrease in these enzymes
ALP, CK, glucose, amylase, lipase
EDTA contamination can appear like acidosis due to __ decrease
bicarbonate (EDTA is an acid! ethylene diamineteraacetic ACID)
overall EDTA contamination can cause artifactual increase in __, decrease in __, __, __ and __
increased: potassium
decreased: Ca, Mg, enzymes and bicarbonate
Best way to collect blood is by
vacutainer
3 direct access routes for blood sample collection
- needle, syringe
- butterfly or extension set
- vacutainer adapter
__ access should be avoided to collect blood because the sample can be contaminated by IV fluids/meds and need to account for deadspace
assisted (catheter, port, etc)
If a sample was taken via assisted access using a catheter where the patient was receiving fluid containing dextrose what might you see in the lab findings
electrolytes will be diluted/low (Na, K, Cl)
glucose will be very high!
Sample handling: samples should be kept __ to minimize cell changes and in indirect contact with ice to prevent __ and __ of cells
cool, freezing, lysis
old blood samples will see
lysis, RBC swelling (MCV, MCHC, PCV), crenation, and platelet activation (MPV, platelet count)
platelet clumps are machine counted as __ and the __ will decrease __
leukocytes, MPV (mean platelet volume)
in old samples, cells clump and clot causing
decrease in all cell types, MCV/MCHC/HCT/PVT
RBC lysis with storage will deacrease RBC count and HCT leading to falsely high __
MCHC (Mean cell hemoglobin concentration)
RBC swell with storage causing a falsely increase __ and __ and decreased __
MCV (mean cell volume), HCT, MCHC (mean cell hemoglobin concentration)
platelet clumping decreases __ and increases __ since small clumps of platelets are seen as one and large clumps are not counted at all
platelet count, MPV (mean platelet volume)
Aged samples result in neutrophil swelling causing a falsely interpreted
left shift/inflammatory leukogram
prolonged sample storage may decrease __ as glycolysis continues in vitro
glucose
prolonged sample storage may increase __ as it leaks from RBC in certain species such as __
potassium
species with K rich RBCs: horses, Japanese dogs (Akita, shiba), camelids, pigs, sheep, some cattle.
Most other dogs and cats do not show this.
sample exposure to light degrades __
bilirubin
Evaporation and freezing (sublimation = evaporation during freezing) causes falsely increased __
electrolytes
When applicable, in monogastrics especially, there should be pre-analytic fasting to prevent post-prandial (after meal) __
lipemia. but can’t fast all p (young animals, horses, cattle)
To rule out analytic factor errors __ should always be evaluated as quality control
blood films
If the analyzer gives results of thrombocytopenia, leukopenia, anemia what should you do?
check blood film for cell clumping (clumped cells are not read appropriately by the analyzer)
What analyzer value should you NEVER trust when running feline blood
automated platelet count!!!
__ can be counted as leukocytes by manual and some automated cell counters, need to correct leukocyte count!
nRBCs (metarubricytes and rubricytes) - these can be normal in low numbers for healthy dogs/cats
NRBC are seen in what dz states
regenerative anemia, lead toxicity, marrow injury/dz, other inflammatory dz
If more than __ nRBC/ 100 WBC are counted, the total WBC count will need to be corrected
5
A dog has 50nRBC/100WBC with a measured WBC count of 9,000/mL. What is the corrected WBC count?
(measured WBC count x 100) DIVIDE (100WBC + nRBC)
(9000 x 100) / (100 + 50) = 6,000/mL
How do you differentiate between a nRBC and a lymphocyte?
nRBC = complete rim of cytoplasm, more eosinophilic cytoplasm lymphocyte = scant cytoplasm
__ is a method of absorptive photometry where reagents are added to produce a color change for biochemistry machine to observe the analytes present (lipemia, hemolysis, icterus, Ca, protein, ALP, Mg, etc)
spectrophotometry “wet chemistry”
__ uses reflective photometry
dry chemistry
Dry chemistry results are affected by
hemolysis, icterus, lipemia, hyperproteinemia, drugs
__ can prevent correct assay results by color interference with spectrophotometric assays
hemolysis
horses, cattle, some dogs have high K with RBCs so hemolysis can cause false increase in
K
__ can be caused by turbidity of sample, if animal has recently eaten, or with hyperlipidemic syndromes
lipemia
lipeamia can interfere with spectrophotometric assays by diluting out substances like __ resulting in falsely decreased concentrations
electrolytes (K, Na, Cl) = ion exclusion effect
__ in blood due to cancer or dz effect the analytic factors by binding analytes causing hyperphosphatemia in dogs
paraproteins
medications like potassium bromide can alter analytic factors causing very very high __ that is not compatible with life and negative anion gap (shouldn’t be negative)
chloride. Actually measuring the bromide with the chloride value
reference intervals define “normal” test results based on a median of ___ of a healthy population
95% +/- 2.5%
There is a __ % chance when measuring analytes that healthy animal will return an “abnormal” test result
5%. Can be normal but outside of the ref interval.
__% chance that 1 test result will be outside the reference interval when 20 analytes are measured
64%
