Blood tube selection Flashcards
What is the difference between plasma and serum?
Plasma - liquid portion of blood that still contains clotting factors
Serum - liquid portion of blood that lack clotting factors due to the clotting process
Why use serum for tests?
Chemical constituents in the circulation - clinical chemistry (not fibrinogen)
Antibodies - serology
How is serum collectedand what tubes can they be in?
Coagulation cascade proceeds, centrifuged and liquid supernatant removed from cells
Tubes:
- plain glass/plastic
- tubes containing clotting activators
- tubes containing gel that forms a sealed barrier between cells and serum so tubes can be posted without need for additional transfer tube
Why use whole blood for tests?
Counting cells - haematology
Some cellular chemistry
What tubes are used for whole blood?
tube contains anticoagulant to stop blood clotting so it remains liquid and complete
Why used plasma for tests?
Chemical constituents in circulation - clinical chemistry (including fibrinogen)
How is plasma collected and stored?
Tube contains anticoagulant to prevent blood clotting so blood remains liquid and complete
Centrifuged and remove liquid supernatant from cells
Other tubes:
- tubes containing beads to help mix the anticoagulant well before clotting starts
- tubes containing gel that forms a sealed barrier between cells and serum so no additional transfer tube needed
What do you need to be aware of when using tubes with anticoagulants?
Can be dry powder coating
Or liquid - beware dilution effect
What are the 2 main mechanisms for in vitro anticoagulants?
Calcium binding
Heparin
Describe different Ca grabbers/chelators and how they work
EDTA:
- irreversibly binds to calcium
Sodium citrate:
- forms ionic complexes with ionised Ca (iCa)
- reduces iCa below that needed for coagulation cascade
- reversible (add Ca to allow coagulation)
Potassium oxalate:
- forms insoluble complexes with Ca ions
Sodium fluoride:
- inhibits glycolysis to preserve glucose
- usually used with oxalate
Why can heparin be used to measure most clinical chemistry
Does not bind anything out of the circulation - no ions have been removed
What happens if you under fill an EDTA tube?
Lead to cell shrinkage due to osmotic effects
What is important about filling a blood citrate tube?
Need to know how much citrate required to overcome clotting so Ca conc in sample must be known - depends entirely on filling to expected volume
Why must you remove the needle from a syringe before dispensing blood into a tube?
Cannot touch inside edges of tubes:
- cannot risk bacterial contamination from other tubes
What are the common reasons for clots in haematology samples?
Delayed transfer to tube so clotting already begun
Inadequate mixing with anti-coagulant
what small animal blood tube is this?
Serum
what small animal blood tube is this?
Serum
what small animal blood tube is this?
EDTA
What small animal blood tube is this?
Heparin
What small animal blood tube is this?
Fluoride-oxalate
What small animal blood tube is this?
Citrate
What large animal blood tube is this?
EDTA
What large animal blood tube is this?
Serum
what large animal blood tube is this?
Heparin
