Practical Lab Flashcards
what is the red blood tube?
serum/”plain” tube
whicg colour is the serum/”plain” tube?
red
what is a serum tube used for?
biochemistry
hormonal assays (e.g. T4)
serology (e.g. antibodies)
what colour is a heparin tube?
orange
OR big with green lid
what is the orange (/big green) tube?
heparin
what is heparin?
anti-coagulant
which is better to use in an emergency, serum or heparin?
heparin - can run quickly
what is the pink (/big purple) tube?
EDTA
what is a heparin tube used for?
in-house biochemistry
which colour tube should be used for haematology?
pink (/big purple)
what is the lilac tube?
citrate
which colour tube contains citrate?
lilac
what is a citrate tube used for?
coagulation profiles
what is the yellow (/big grey) tube?
oxalate
what colour are oxalate tubes?
yellow (/big grey)
what is oxalate used for?
glucose
are oxalate tubes used regularly?
rarely used - glucose measured in biochemistry (heparin)
which type of blood tube doesn’t contain clotting factors?
serum tubes
why do all the blood tubes (minus serum) obtain plasma, rather than serum?
contain an anticoagulant
what is the difference between serum and plasma?
serum is the liquid that remains after clotting of blood
plasma is the liquid that remains when anticoagulant is added to prevent clotting
which blood tube should always be filled last?
EDTA
why should EDTA always be filled last?
contamination with EDTA in other samples will prevent clotting - EDTA chelates calcium
how does EDTA contamination affect biochemistry?
low calcium
high potassium
what does a reference range mean?
includes 95% of healthy animals
which blood tube should you elect for emergency biochemistry?
heparin (orange/big green)
how can we tell whether a blood result is a mild, moderate or marked change from the reference?
calculate value of the reference range (e.g. 58-78 = 20)
if within reference range either side = mild
more than 20 either side = moderate
more than 40 either side = marked
why might an animal have high ALT?
primary hepatopathy
secondary to cholestasis
artefact
due to muscle damage
what can we check to differ between liver and muscle damage in the presence of high ALT?
creatinine kinase
what are the markers of hepatocellular damage?
ALT, AST, GLDH, SDH
what are the markers of cholestasis?
ALP, GGT
what can we look at to establish function of the liver?
substances produced in the liver
substances conjugated and excreted by the liver
what substances are produced in the liver?
cholesterol
urea
glucose
albumin
some globulins
coagulation factors
which substances are conjugated and excreted by the liver?
bile acids
bilirubin
what can cause primary hepatocellular disease?
trauma
toxins, drugs
inflammation/infection
neoplasia
intrahepatic cholestasis
bile toxicity
what can cause secondary hepatocellular disease?
you name it - the liver is very sensitive to secondary causes
which increased liver parameters reflect decreased hepatic function?
bilirubin
bile acids
which decreased liver parameters reflect decreased hepatic function?
albumin
cholesterol
urea
glucose
clotting factors
what is the result of xylitol toxicity?
acute hepatic failure
hypoglycaemia
how can xylitol toxicity be treated?
multiple plasma transfusions
vitamin K therapy
liver supportive treatment
gastroprotective treatment
fluid therapy
antibiotics
what are the features of a stress leukogram?
neutrophilia
monocytosis
lymphopaenia
eosinopaenia
how can the features of a stress leukogram be remembered?
SMILED
Segmented nucleus (neutrophilia)
Monocytes Increased
Lymphocytes and Eosinophils Decreased
does a stress leukogram need to have all 4 derangements?
no
what are acanthocyes?
spiculated red cells
when are acanthocytes seen?
almost exclusively seen as an artifact - usually from old blood
can be from toxins effects on cell membranes
what is anisocytosis?
different cell sizes
what urine concentration is indicative of kidney disease?
isosthenuria
what is the treatment for antifreeze toxicity?
supportive care - IVFT important
ethanol IV
why might there be an absence of stress leukogram?
chronic disease
immunosuppression
bone marrow disease
what biochemistry abnormalities will likely be seen with kidney disease/injury?
marked azotemia (creatinine)
marked increase in ALT
electrolyte derangements - marked hypocalcaemia
mild hyponatremia/hypochloremia/hyperkalaemia
what is cytology?
screening test to look for cells in:
fluid (BAL, CSF, synovial fluid, body cavities)
tissue samples (lumps, bumps, LNs)
what clinical information do we need when presented with a lesion?
clinical history and lesion evolution
any previous treatment
characteristics of the lesion
how can we define the characteristics of a lesion?
localisation
dimension
firm/soft
painful/non-painful
ulcerated/non-ulcerated
cutaneous/sub-cutaneous
adherent/non-adherent
how does the aspirate look?
when would you use suction technique for FNA?
hard cutaneous or subcut masses
bone lesions
when non-suction technique is unsuccessful
when would you use non-suction technique for FNA?
soft cutaneous or subcut masses
lymph nodes
vascular lesions/organs
what is important to remember when performing suction FNA?
make sure to relax plunger before exiting mass in order to avoid pulling debris from more superficial layers of tissue
what is the aim of the squash/smear technique for FNA cytology?
trying to create a monolayer
what are the idea techniques for creating FNA slides?
line (like blood smear)
squash
twist
star and spatter not ideal but sometimes necessary/no choice
what other collection methods may be used for cytology?
impression smear
scraping (mites)
ear swab - imprint (roll)
biopsy - imprint
what might we see from an ear swab which indicates infection?
malassezia fungis - yeast
peanut-shaped
is malassezia a normal finding?
present in low numbers on normal skin, less normal in ears
multiple organisms per HPF indicate significant infection
what should we do with the cytology slides after collection?
dry slide rapidly - air fixation/cool hairdryer
make sure completely dried before staining /packaging to send away
label (pencil) the smears - ID/site/date
what is the most common staining technique in practice?
Diff-Quick
what other staining techniques may be used in practice?
Giemsa/modified wright
methylene blue
toluidine blue (MCTs)
ziehl/nielsen
what are the different solutions in Diff-Quick and what are their roles?
A - methanol - fixation
B - eosin - eosinophilic (base) staining
C - methylene blue - basophilic (acid) staining
what are the considerations for Diff-Quick staining?
replace stains regularly (esp methylene blue)
keen a clean and “dirty” set - separate set for derm cytology
thick smears may require longer staining times and more time to dry
what is the magnification of the eyepiece itself in a microscope?
x10, so
x10 = x100
x40 = x400 etc
what can be seen under low magnification (x10)?
cellularity
preservation
staining
haemodilution
cell distribution
background
what does cell preservation refer to?
how well the staining process has worked
what can we look at under high magnification (x40)?
cellular vs non-cellular elements
inflammatory vs neoplastic
malignant vs benign
what can we look at under the highest magnification (x100)?
presence of cytoplasmic granules
nuclear detail
presence of pathogens - bacteria, fungi, protozoa
what do neutrophils on cytology indicate?
inflammation
what do normal neutrophils look like?
crisp nuclear outlines with dark purple chromatin
cytoplasm is pale, clear to slightly eosinophilic (pink)
what do degenerate neutrophils indicate?
usually indicate presence of bacterial infection - affected by toxic change
what do degenerate neutrophils look like?
loss of segmentation
lighter coloured ‘fluffy’ nuclear chromatin and a swollen appearance
can we assume no infection if degenerate neutrophils present but no bacteria?
no - culture if suspicious
what are the advantages of cytology?
easy, quick and cheap
relatively non-invasive
several collection methods and smear techniques
can be stained in practice
is cytology confirmatory?
no - histology required
how can we ensure results produced in the lab are reliable?
correct setup of the system
maintenance of analysers and system
accurate interpretation of results
checks carried out to ensure the values are acceptable
accurate record-keeping
what are the advantages of in-house labs?
fast turn-around time
potential for improved monitoring
smaller volume of sample needed
available OOH
available in more remote areas
may save costs
what are the 2 major factors affecting lab results?
biological factors
analytical factors
what are the overall biological factors which might affect total variability?
inter-individual factors
intra-individual factors
what are inter-individual factors?
inherent differences between groups of animals due to species, breed, age and/or sex
what are intra-individual factors?
transient differences in the same animal, often due to environmental/external factors
give some examples of intra-individual factors
diet (e.g. recent meal)
stress/excitement
reproductive status/lactation
drugs
method/site of blood sampling
what are the overall analytical factors which can affect total variability?
pre-analytical
analytical
post-analytical
give some examples of pre-analytical factors
poor blood sampling technique
haemolysed, lipaemic or icteric plasma
wrong anticoagulant:blood ratio
transportation
storage
how should postal samples be processed?
50mL limit
sealed container in leakproof bag
absorptive padding
all packaged in rigid container
what are the main types of analytical equipment?
laboratory vs patient-side (e.g. glucometers)
results vary significantly and therefore cannot be directly compared
what are analytical factors?
factors which can cause variation/error during the analysis of the sample and influence the final result
give some examples of analytical factors
equipment - proper function, maintenance etc
technician - correct training, pipetting etc
analytical procedure - validated technique, reagents, calibrations
laboratory - temperature, humidity etc
is quality control mandatory?
no - voluntary process
there are no regulations, just recommendations
what happens during quality control?
control material of known composition is measured to check the accuracy of the analytical process
when is quality control performed?
during the analysis to ensure the validity of the result
is control the same as calibration?
no - controls are not to calibrate the machine but to check the tests are being run accurately
what should you do if a control fails?
check for obvious problem (reagent depletion/expiry, mechanical faults, clots)
use another aliquot of control materials
repeat control
what should you do if the control fails again?
use new reagent, recalibrate equipment, repeat control
run routine machine/instrument maintenance and repeat control assay
consult manufacturer
what are the post-analytical factors which can affect total variability?
transfer of results to patient record
archiving results
storing specimen (e.g. for follow-up tests)
