Sample collection and processing Flashcards
(30 cards)
What is the accuracy of any test procedure dependent on?
Quality of the specimen
- How and when it was collected
- care given to preservation and transportation to the lab
What is a red top tube and what is it used for?
Plain (clotted)
For general biochemistry, bile acids, serology and endocrinology
What is a lavendar top tube and what is it used for?
EDTA (whole blood)
For Haematology
What is a green top tube and what is it used for?
Heparin (plasma)
For Biochemistry of plasma and reptilian/avian haematology of whole blood
What is gray top tube and what is it used for?
Oxalate/Fluoride (whole blood or plasma)
For glucose
What is a light blue top tube and what is it used for?
Sodium citrate (whole blood or plasma)
For clotting times
-PT, APTT and VWB factor Ag
How much more blood do you need to take when making a serum sample?
2 1/2 times the needed volume
If you want 4ml of serum for a test, how much blood will you need to take?
10ml of blood
How do you collect and prepare blood for a serum test?
Draw needed amount into the red top tube Allow to clot 15-20 minutes Centrifuge Aspirate the supernatant (serum) Place in a plain tube
How much plasma should you draw into a tube for testing?
The marked amount on the tube to get the correct anticoagulant:blood ratio
How do you collect and prepare blood for a plasma test?
Draw blood from animal to full volume marked on the tube Invert vacutainer several times Centrifuge straight away Aspirate the supernatant (serum) Place in a plain tube
What does an EDTA tube contain and what is its effect on cells?
Contains potassium salt of ethylene-diamine-tetra-acetic acid
It preserves cell morphology
In an EDTA tube is the ratio of blood to anticoagulant important?
Yes, very
What 3 things are an EDTA tube used for?
Collect blood for -
Haematological analysis
PCV
Blood film evaluation
What are the 5 consequences of underfilling an EDTA tube?
Shrinkage of RBC’s
Artefactual RBC shape and decrease in PCV and MCV
Discordance between PCV and haematocrit HCT
Elevated protein on refractomoeter
If anticoagulant is liquid it will dilute blood and lead to low values
What are the 3 consequences of overfilling an EDTA tube?
Might clot
Affect results
Can cause obstruction of tubing in instruments
How should you transport blood samples?
In an esky with an ice block but making sure that the sample doesn’t directly contact the ice - freeze lysis
Make blood smear on site and transport separately
Why is a collection with a vacutainer preferable to syringe?
Because a vacutainer is manufactured with the appropriate negative pressure for venous draw
If you are collecting blood by a syringe instead of a vacutainer, what 2 things do you need to do?
Remove the needle prior to transferring blood to the collection tube
Avoid excessive vacuum pressure
When collecting blood by a syringe how do you avoid excessive vacuum pressure and what are 3 consequences of excessive vacuum?
Using appropriate syringe size and withdrawal pressure
- Haemolysis
- Interferes with biochemistry tests measured by spectrophotometer
- Erroneous haematology results
What is the importance of doing a ‘clean’ venous puncture?
So you don’t activate clotting which will interfere with results
What should you do if you get a ‘haemogram tsunami’
Throw it out
Sample has clotted and you cannot use it
What order should you draw tubes in? (6 tubes)
Red - plain Blue - sodium citrate Tiger top - gel separator Green - heparin Lavendar - EDTA Grey - Sodium fluoride
Why is the order of draw into tubes important?
To avoid the carryover of additives which can affect results
