intro to blood tube selection

Question 1

what is serum

Answer 1

the liquid remaining from the blood sample after it has been allowed to clot and spun. NO FIBRINOGEN (because in the clot)

Question 2

what information can be gleaned from serum

Answer 2

• chemical constituents in the circulation
• antibodies

Question 3

what is whoe blood

Answer 3

blood that has not been allowed to clot or spun.

Question 4

what can be gleamed from whole blood

Answer 4

• cell counts (hematology)
• certain cellular chemistry

Question 5

what is plasma

Answer 5

the liquid spun off of blood that has not been allowed to clot (fibrogen still included)

Question 6

what can be gleaned from plasma

Answer 6

• chemistry constituents in the circulation
• fibrogen info

Question 7

what are the main coagulation cofactors that are targeted in anticoagulents

Answer 7

• calcium ion
• anti thrombin

Question 8

Describe how EDTA tubes prevent clotting

Answer 8

• calcium chelator
• tightly binds calcium not reversible
• applied to tube as dry power coat (K salt)

Question 9

describe how citrate tubes prevent clotting

Answer 9

• forms ionic complexes with ionised calcium
• reduces iCa below that needed for coagulation cascade
• reversible
• can add ca back into sample to allow coagulation to proceed
• liquid in bottom of tube

Question 10

what are citrate tubes used for and why

Answer 10

• measuring coagulation times and factors (just add Ca back in for coagulation to proceed)
• transfusions (citrate metabolised in vivo)

Question 11

how do oxalate tubes work to prevent clotting

Answer 11

inhibits blood coagulation by forming insoluble complexes with calcium ions which is necessary for coagulation

Question 12

how do fluoride tubes work for preventing clotting and what are they commonly used for

Answer 12

• inhibits RBC metabolism and bacterial action
• inhibits glycolysis
• preserves glucose samples

Question 13

describe how lithium heparin tubes work

Answer 13

• depends on presence of anti-thrombin 3 in the smaple
• promotes AT ability to bind (inactivate) factor 10a
• locks AT and thrombin together
• lithium as the salt so that Na and K levels can still be measured
• used for clinical chem

Question 14

why is proper tube fill important

Answer 14

concentrations of anticoagulant:
- EDTA causes osmotic effects and can shrink cells if under filled leading to mis counting in machines
- citrate depends on having just the right amount of calcium binding, if over fill there will be enough calcium for clotting to proceed
- liquid anticaugulants can dilute samples

Question 15

what is the fill order of blood tubes and why is fill order relevent

Answer 15

1. culture
2. citrate
3. serum
4. serum seperator
5. heparin
6. EDTA
7. fluoride oxalate

important to follow order so no cross contamination occurs (dont want EDTA anticoagulant on sample you want to clot or if you have a clotting stim dont want that in and EDTA)