Whole blood is necessary for most hemolytic investigations the sample must therefore be mixed with an anticoagulant to prevent coagulation. Anticoagulants are defined ad substances which prevent blood clotting/coagulation allow separation of the blood into cellular and liquid (plasma) components. Generally plasma contains coagulation factors.
The common hematological anticoagulant is listed below:
Double oxalate
0.5 anticoagulant for 5ml of blood
Chemical Action : This anticoagulant removes the free calcium ion from solution through the addition of ammonium and potassium oxalate. Calcium is precipitated as insoluble calcium oxalate.
Preparation:
- 1–2 gram ammonium oxalate and 0.8 gm potassium oxalate are dissolved in 100ml of distilled water.
- 0.5 ml of this solution is added to each of a series of tubes and evaporated to dryness at 37°C higher temperature decompose the exalted.
Use :- Blood taken into this anticoagulant is unsuitable for morphological examination, the red cells commerce to crenate and the white exhibit bizarre nuclear patterns.
Ethylene Diamine Tetra Acetic Acid (EDTA)
Ethylene Di amine Tetra acetic acid (Edta ) can be found in three salt forms:
- Tri potassium EDTA
- Di sodium EDTA
- Di Lithium EDTA
Also, Edta can be crystalline or liquid . liquid EDTA tubes require specific filing volume to avoid dilution effect. So, blood : Anticoagulant ratio must be maintained (This is applicable to all anticoagulants ). EDTA is also known as versene or sequences. EDTA acts by chelating ionized calcium . Generally tri potassium EDTA is better than di sodium EDTA and di — Lithium EDTA.
Always be sure to mix blood with anticoagulant in an manner that guarantee proper complete mixing. By gentle repeated inversion since this may cause hemolysis and disintegration of cells and the final effect will be erroneous low result for cellular components of blood EDTA is the most commonly used anticoagulant in the hematology laboratory and is the anticoagulant of choice for the CBC.
Heparin
Heparin is an acid Mucopolysaccharide it acts by complexing with antithrombin to prevent blood clotting (antithrombin is one of the natural/physiological inhibitors of blood coagulation). It is not suitable for blood films staining since it gives too blue coloration to the background when films are stained with rowmanwosky stains also heparin May cause leukocyte and platelets, clumping this is why heparin is not suitable for routine hematology.
Sodium Citrate
Sodium citrate has been used as an anticoagulant to stabilize blood and blood products for over 100 years, presumably by sequestering Ca(++) ions in vitro. Anticoagulation of blood without chelation can be achieved by inhibition of the contact pathway by corn trypsin inhibitor (CTI).
Sodium Fluoride
This anticoagulant is used for preparing blood specimens for the determination of glucose and urea in plasma by non enzymatic methods. Fluoride inhibits glycolytic enzymes and thereby prevents loss of glucose during transportation or delay in specimen handling as fluoride is not a strong anticoagulant it is mixed with oxalate.