Sample collection and processing

Question 1

What is the accuracy of any test procedure dependent on?

Answer 1

Quality of the specimen

• How and when it was collected
• care given to preservation and transportation to the lab

Question 2

What is a red top tube and what is it used for?

Answer 2

Plain (clotted)

For general biochemistry, bile acids, serology and endocrinology

Question 3

What is a lavendar top tube and what is it used for?

Answer 3

EDTA (whole blood)

For Haematology

Question 4

What is a green top tube and what is it used for?

Answer 4

Heparin (plasma)

For Biochemistry of plasma and reptilian/avian haematology of whole blood

Question 5

What is gray top tube and what is it used for?

Answer 5

Oxalate/Fluoride (whole blood or plasma)

For glucose

Question 6

What is a light blue top tube and what is it used for?

Answer 6

Sodium citrate (whole blood or plasma)
For clotting times
-PT, APTT and VWB factor Ag

Question 7

How much more blood do you need to take when making a serum sample?

Answer 7

2 1/2 times the needed volume

Question 8

If you want 4ml of serum for a test, how much blood will you need to take?

Answer 8

10ml of blood

Question 9

How do you collect and prepare blood for a serum test?

Answer 9

Draw needed amount into  the red top tube
Allow to clot 15-20 minutes
Centrifuge
Aspirate the supernatant (serum)
Place in a plain tube

Question 10

How much plasma should you draw into a tube for testing?

Answer 10

The marked amount on the tube to get the correct anticoagulant:blood ratio

Question 11

How do you collect and prepare blood for a plasma test?

Answer 11

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

Question 12

What does an EDTA tube contain and what is its effect on cells?

Answer 12

Contains potassium salt of ethylene-diamine-tetra-acetic acid
It preserves cell morphology

Question 13

In an EDTA tube is the ratio of blood to anticoagulant important?

Answer 13

Yes, very

Question 14

What 3 things are an EDTA tube used for?

Answer 14

Collect blood for -
Haematological analysis
PCV
Blood film evaluation

Question 15

What are the 5 consequences of underfilling an EDTA tube?

Answer 15

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

Question 16

What are the 3 consequences of overfilling an EDTA tube?

Answer 16

Might clot
Affect results
Can cause obstruction of tubing in instruments

Question 17

How should you transport blood samples?

Answer 17

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

Question 18

Why is a collection with a vacutainer preferable to syringe?

Answer 18

Because a vacutainer is manufactured with the appropriate negative pressure for venous draw

Question 19

If you are collecting blood by a syringe instead of a vacutainer, what 2 things do you need to do?

Answer 19

Remove the needle prior to transferring blood to the collection tube
Avoid excessive vacuum pressure

Question 20

When collecting blood by a syringe how do you avoid excessive vacuum pressure and what are 3 consequences of excessive vacuum?

Answer 20

Using appropriate syringe size and withdrawal pressure

• Haemolysis
• Interferes with biochemistry tests measured by spectrophotometer
• Erroneous haematology results

Question 21

What is the importance of doing a ‘clean’ venous puncture?

Answer 21

So you don’t activate clotting which will interfere with results

Question 22

What should you do if you get a ‘haemogram tsunami’

Answer 22

Throw it out

Sample has clotted and you cannot use it

Question 23

What order should you draw tubes in? (6 tubes)

Answer 23

Red - plain
Blue - sodium citrate
Tiger top - gel separator
Green - heparin 
Lavendar - EDTA
Grey - Sodium fluoride

Question 24

Why is the order of draw into tubes important?

Answer 24

To avoid the carryover of additives which can affect results

Question 25

What biochemistry result pattern will appear if there has been contamination with EDTA salt? And why is this?

Answer 25

Severe hypocalcaemia and hyperkalaemia that isn’t compatible with life
Hypomagnesaemia
Low ALP
Why?
-EDTA is a chelating agent and binds divalent cations (Ca, Mg, Zn), Mg and Zn are cofactors to measure ALP

Question 26

What are the 3 most common ways that EDTA can contaminate a sample?

Answer 26

Backflow (pressure in vein less than vacutainer)
Decant
EDTA plasma used instead of serum

Question 27

Does plasma and serum contain fibrinogen?

Answer 27

Plasma contains fibrinogen, serum does not

Question 28

Why should an animal ideally be fasted 12hours prior to collection?

Answer 28

To avoid lipaemia

Question 29

What can lipaemia in a sample cause?

Answer 29

Haemolysis - the sample is less stable
Haemolysis and lipaemia both -
Interfere with spectrophotometer results
Erroneous haematology results

Question 30

What 3 things can be in blood and interfere with laboratory testing? (think about solutes)

Answer 30

Haemolysis
Lipaemia
Hyperbilirubinemia (Icterus)