Anticoagulants

Ethylene diamine Tetra-acetic Acid (EDTA)

This is the anticoagulant of choice for the FBC. di-Na and di-K salts are solids and tri-Na is the liquid form.

Mode of Action
EDTA chelates calcium ions to form a soluble complex

Uses

  • Haematology Profile
  • EDTA blood smears

Concentration
1.5mg/mL +/- 0.35mg/mL
If less blood is collected than fills the complete tube containing the anticoagulant shrinkage of the RBCs and degenerative changes (eg. swelling of the Plts) will occur - this will affect MCV and Hct etc.

Stability
Blood smears should be made within 3hrs of collection (to avoid changes in morphology)

Disadvantages

  • EDTA cannot be used for coagulation studies (as it chelates calcium)
  • Platelets can sometimes be seen to satellite neutrophils
  • EDTA effects the function of fibrinogen (can sometimes be seen as stranding of fibrin on a blood smear)

Sodium Citrate

This is a liquid anticoagulant.

Mode of Action
Removes calcium ions by forming a soluble calcium citrate complex.

Uses
  • Coagulation studies   9:1 - blood:citrate
  • ESR   4:1 - blood:citrate
  • Reticulocyte count
  • Heinz body detection
  • Acts as both a diluent and an anticoagulant

Concentration
0.109mg/mL

Disadvantages

  • Cannot use for FBC because of the dilution factor

Heparin

This anticoagulant is an acid mucopolysaccharide which is considered to be the anticoagulant of reference for red cell morphology.

Mode of Action
Stops the formation of thrombin from prothrombin therefore stopping formation of fibrin from fibrinogen

Uses
  • Enzyme studies
  • Cell cultures
  • Osmotic fragility testing
Concentration
15IU/mL +/- 2.5IU/mL

Disadvantages
  • Relatively Expensive
  • Can give a blue background to blood films
  • Platelet aggregation

Glossary

Hb
Haemoglobin. This abbreviation is comonly used to represent the concentration of haemoglobin in the blood.

Hct
Haematocrit. The Hct is the volume of packed red cells in whole blood, in relation to the total volume of the whole blood specimen (L/L).

MCV
Mean Cell Volume. The MCV indicates the average cell volume of red cells in femtolitres (fl).

 
haematocrit (L/L)
MCV (fL) =
------------------
 
RCC (x 1012)

Plt
Platelets. Discoid-shaped, anuclear bodies which are necessary for maintaining the haemostatic mechanism.

RCC
Red Cell Count. This abbreviation usually refers to the total number of red cells (erythrocytes) in whole blood (million/mL)

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