PRE COLLECTION VARIABLES, Lecture notes of Chemistry

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WHAT IS SERUM?

WHAT IS PLASMA?

PRE COLLECTION

VARIABLES

ANTICOAGULANTS

A. EDTA (ethylenediaminetetraacetic acid)

B. Citrate

C. Heparin

D. Oxalate

E. Fluoride

CITRATE

White-top tubes also contain EDTA and gel. They are used

most often for molecular diagnostic testing of plasma.

CITRATE – combines with calcium in a non-ionized form

 For coagulation testing, a light blue–top tube containing

0.105 M or 0.129 M (3.2% and 3.8%) sodium citrate is

commonly used because it preserves the labile

coagulation factors.

 BLOOD TO ANTICOAG RATIO 9:

OXALATE

(BLACK)

o

combines with calcium to form an insoluble salt

o

Available as sodium, potassium, ammonium and

lithium oxalate

Black-top tubes also contain buffered sodium citrate

and are generally used for Westergren sedimentation

rates. They differ from light blue–top tubes in that the

ratio of blood to anticoagulant is 4:1 in the black-top

tubes and 9:1 in the light blue–top tubes.

Lithium heparin: glucose, BUN, ionized

calcium, pH and blood gas

analysis, creatinine,

cytogenetic studies and

potassium test

Sodium heparin: injectable form for

anticoagulant therapy;

trace elements, lead and

toxicology

FLUORIDE

(GRAY)

Gray-top tubes

Forms weakly dissociated calcium components

Conc: 10mg/mL of blood

are generally used for glucose measurements because they

contain a preservative or antiglycolytic agent, such as sodium

fluoride , which prevents glycolysis for up to 3 days.

In bacterial septicemia, fluoride inhibition of glycolysis is

neither adequate nor effective in preserving glucose

concentration.

REFLUX  backflow of blood from the tube into the patient’s vein that

occur if the blood in the tube is in contact with the needle during blood

flow.

*To prevent reflux, the patient’s arm must be in a downward position so

that the collection fills from bottom up.

ADDITIVE CARRY-OVER

 Occur when blood in an additive tube touches the

needle during venipuncture or during transfer from a

syringe.

 Additive in the blood that is on or within the needle

can then be transferred to the next tube drawn or filled.

 it is less likely to occur if tubes fill from the bottom

up, which keeps tube contents away from the needle

CLSI ORDER OF DRAW (Bishop)

1. Sterile tube (e.g., blood culture)
2. Coagulation tube (e.g., blue top)
3. Serum tube with or without clot activator, with or without gel separator

(e.g., red top)

4. Heparin tube with or without gel separator (e.g., green top)
5. EDTA tube with or without gel separator (e.g., lavender top, pearl top)
6. Glycolytic inhibitor tube (e.g., gray top)