Sample Collection Flashcards
what are the 6 advantages of an in-house lab?
fast turn around out of hours improved patient monitoring and care available in more remote areas smaller sample volume so less invasive may save costs
what are the 6 main pre-analytical factors which have a big effect on lab results
poor sampling haemolysed, lipaemic or icteric plasma wrong anti-coagulant wrong anticoagulant/blood ratio transportation of sample storage of sample
what pre-analytical factors can cause haemolysis?
collection method - vein collapse or over enthusiastic sampling!
what can avoid lipaemic samples?
fasted samples
what should a sample be labelled with?
patients number (internal samples) or patient name/owner name
what must be included on the form for the external lab?
identify samples that were collected
identify tests required and send correct samples for these tests
identify clinician
a basic history
drug history
previous reference of lab if known/relevant
what should be included on the basic history for the external lab form?
presentation and other lab and imaging findings
if using sample for drug monitoring what should be included?
time of administration
what is the fluid limit for sending samples by post?
50ml
how must samples be packaged for posting?
sealed container
padded with enough material to absorb any leaks
sealed in a leak-proof bag
put inside a solid container
what must not be sent by post?
class 4 pathogens
what must be alerted for during postage and for the recipient?
possible zoonoses
cytotoxic samples
what tests is blood often sampled for?
haematology
biochemistry
serology
PCRs
what must be checked before sample collection of blood?
type of tube required and volume of blood/plasma
why should 3x more than plasma volume required be collected during blood sampling?
PCV - approx half of the sample will be cells
how can haemolysis and platelet clumping be avoided?
performing clean sticks (first time) without creating vacuum/collapsing veins
what should happen if sample collection was difficult?
be noted on history and passed onto lab
what assays must be taken at specific timings?
dynamic assays e.g. bile acid stimulation
when should drug assays be taken?
at either peak (highest expected level) or trough (lowest expected level)
what assays can lipaemia affect?
total proteins, bile acids and bilirubin
what effect can stress of animals on collection have?
altered parameters
where can blood be collected from in all species?
jugular vein
what are the main collection veins in small animals?
cephalic and saphenous vein
what vein is used for collection in birds?
cubital/wing
what arteries can be used for blood collection?
digital
femoral
carotid
what capillaries can be used for blood sampling?
skin especially ears
what does needle size and length depend on?
vessel site and diameter - in order to reduce haemolysis
what needle should be used for phlebotomy?
widest gauge practicable and humane to reduce haemolysis
what needle should be used for cystocentesis?
smallest gauge possible to reduce risk of bladder tear
what direction should the needle be directed during cystocentesis?
caudally
what needles can be used during mass aspiration?
using a variety of sizes and active aspiration/needle redirection
what levels of leukocytes can increase during stressful sampling?
neutrophils and lymphocytes (neutrophillia and lymphocytosis)
why do neutrophil and lymphocyte level increase under stressful sampling situations?
increased blood pressure sweeps mature cells from marginal pool into circulation
what can clots in the syringe lead to?
false thrombocytopenia
what can elevate PCV/haematocrit in horses?
splenic contraction under stress
what can restraint lead to?
elevated creatinine kinase
what can be activated by stressful sampling?
clotting cascade by tissue factor
how is plasma formed from whole blood?
anti-coagulant and centrifugation
how is serum formed from whole blood?
no anticoagulant
allowed to clot before anything happens to it
are reference ranges different for serum and plasma?
yes
does serum have higher or lower total proteins than plasma?
lower
can serum be spun straight away?
no - must be left to clot?
should serum be sent spun or unspun?
spun as reduces risk of haemolysis
what anticoagulant can be used with plasma?
any - EDTA, heparin, fluoride and oxalate
what must happen to plasma samples immediately?
must be spun
what situation is plasma sampling useful in?
emergancy - quick
what analyses is plasma not recommended for?
direct bilirubin
bile acids
protein electrophoresis
why does plasma affect some analyses?
background fibrinogen content disturbing some reactions
what sample tubes can be used for biochemistry?
plain tube/serum
heparin
oxf
what sample tubes cannot be used for biochemistry?
citrate
EDTA
how should a plain/serum tube be used for biochemistry?
allowed to clot and then serum separated
what can a plain tube/serum not be used for?
fibrinogen
what must a plain tube/serum be used for?
bile acids
haptoglobin
protein electrophoresis
how does heparin stop clot formation?
increases action of antithrombin III which stops clot formation
what is an Oxf tube used for?
glucose testing as prevents use of glucose by RBC
why is an EDTA tube not suitable for biochemistry?
contains potassium and takes up calcium so will give false high K+ and false low Ca2+
why can a citrate tube not be used for biochemistry?
uses (chelates) all calcium as it bind calcium to prevent clotting
what effect can EDTA contamination have on results?
increase potassium
reduce Ca2+
affect some enzymes as their cofactors are chelated
how should all samples be handled?
seperate serum/plasma from cells by centrifugation
refrigerate if long test delay
what assays are affected by sunlight?
bilirubin
what form are reagents in in dry chemistry analysers?
‘dry’ form
what happens to serum/plasma samples in ‘wet’ biochemistry analysers?
mixed with liquid reagents
what are the advantages of ‘wet’ chemistry analysers?
liquid reagents are cheaper than dry
what are the negatives of ‘wet’ chemistry analysers?
shorter storage life
more technically challenging
what are common issue with blood smears?
too much blood used too little blood used bunny hopping/hesitation lifting the spreader off running out of slide
what tube should be used for part of the urine sample if the vets need cytology?
EDTA
what is the best sample technique for urine culture?
cystocentesis
do cystocentesis or catheter samples require storing in boric acid tubes?
no as should not be contaminated with bacteria
what is FNA?
fine needle aspirate
can vet nurses perform FNA?
yes as long as no entry into body cavity
describe the technique for FNA?
mass is isolated between finger and thumb
needle is placed into it and cells are aspirated
plunger of the syringe (if used) should be released before the needle is withdrawn
what are the 2 types of FNA technique?
non-asperative
asperative
describe non-asperative FNA technique
needle is inserted at a number of different angles into the mass and fluid is extracted
describe aspertive FNA technique
syringe is attached to needle and used to draw out cells from mass
how is FNA sample transfurred to a slide?
air drawn into syringe and then fluid/cells forced out by depression of plunger over slide
what slide preparation is used for FNA samples?
squash - sample is compressed between 2 slides
when should smears of fluid for microscopic evaluation be made?
ASAP after sampling
what are EDTA tubes used for for fluid samples?
cell counts on analyser
what must be done with fluid samples with low cell counts?
centrifuged and smear performed with re-suspended pellet
what is a plain tube used for during fluid sampling?
Total proteins on refractometer or analyser
what are sterile tubes used for during fluid sampling?
culture
what must happen to slides before transport/packaging?
be dried as quickly as possible (can use a hair dryer) before being stained, stored or packed for transport
what should be avoided when performing ultrasound fine needle aspirate?
using ultrasound gel - use surgical spirit instead
what effect does formalin have on samples?
turns everything blue and cellular detail is lost
