What is an Anticoagulants?
The anticoagulants are a substance that prevents blood clotting by inhibiting coagulation factors.
It is essential in laboratory settings to maintain blood in a fluid state for various diagnostic tests.
Types of Anticoagulants
Anticoagulants are categorized based on their mechanism of action. The major types include:
- Ethylene Diamine Tetraacetic Acid (EDTA)
- Heparin
- Double Oxalate
- Trisodium Citrate
- Sodium Fluoride
Let’s explore each type in detail.
1. Ethylene Diamine Tetraacetic Acid (EDTA)
EDTA, also known as Sequestrene or Versene, is the most commonly used anticoagulant in hematology. It works by binding calcium ions, preventing blood clot formation.
Types of EDTA
- Disodium salt EDTA
- Dipotassium salt EDTA (Recommended by the International Committee for Standardization in Hematology due to higher solubility.)
Properties & Uses of EDTA
| Property | Details |
|---|---|
| Concentration | 1.5 mg/ml of blood |
| Mode of Action | Chelation of calcium |
| Uses | Complete Blood Count (CBC), Blood smear, Hemoglobin electrophoresis, Sickling test, Hemoglobin estimation |
| Disadvantage | Not used for coagulation tests; causes pseudothrombocytopenia in hematology analyzers |
| Form | Dried powder |
2. Heparin
Heparin is a naturally occurring anticoagulant that prevents clot formation in blood vessels by inhibiting thrombin and fibrin formation.
Types of Heparin
- Sodium Heparin
- Lithium Heparin (Preferred in clinical biochemistry due to minimal interference in tests.)
- Ammonium Heparin
Properties & Uses of Heparin
| Property | Details |
|---|---|
| Concentration | 15U/ml of blood |
| Mode of Action | Inhibits thrombin and fibrin formation |
| Uses | Erythrocyte Sedimentation Rate (ESR) estimation (Wintrobe method) |
| Disadvantages | Causes blue background in blood smears; expensive |
| Form | Dried powder |
3. Double Oxalate
Double Oxalate is a combination of Ammonium Oxalate and Potassium Oxalate in a 3:2 ratio. It prevents coagulation by binding calcium.
Properties & Uses of Double Oxalate
| Property | Details |
|---|---|
| Concentration | 3:2 ratio (Ammonium Oxalate: Potassium Oxalate) |
| Mode of Action | Chelation of calcium |
| Uses | Osmotic fragility test, Immunophenotyping |
| Disadvantage | Causes RBC crenation, making it unsuitable for blood films |
| Form | Dried powder |
4. Trisodium Citrate
Trisodium Citrate is the preferred anticoagulant for coagulation studies as it preserves clotting factors.
Types of Trisodium Citrate
- 3.2% Trisodium Citrate (Preferred for accurate coagulation studies.)
- 3.8% Trisodium Citrate (Used in ESR tests.)
Properties & Uses of Trisodium Citrate
| Property | 3.2% Trisodium Citrate | 3.8% Trisodium Citrate |
|---|---|---|
| Concentration | 1.109 mg/ml of blood | 1.109 mg/ml of blood |
| Mode of Action | Chelation of calcium | Chelation of calcium |
| Uses | Coagulation profiles (PT, INR, APTT, D-Dimer) | ESR estimation |
| Form | Liquid anticoagulant | Liquid anticoagulant |
| Anticoagulant-to-Blood Ratio | 1:9 | 1:4 |
5. Sodium Fluoride
Sodium Fluoride is a glycolysis inhibitor used for blood glucose estimation. It is commonly combined with Potassium Oxalate or EDTA.
Properties & Uses of Sodium Fluoride
| Property | Details |
|---|---|
| Concentration | 2.5 mg/ml of blood |
| Mode of Action | Chelation of calcium & inhibition of glycolysis |
| Uses | Blood glucose estimation, HbA1c test |
| Combination | Used with Potassium Oxalate or EDTA |
Key Takeaways
- EDTA is best for hematology tests (CBC, Blood smear, Hb analysis).
- Heparin is used in biochemical tests but not in blood smears due to staining issues.
- Double Oxalate is used in osmotic fragility tests but not in blood films.
- Trisodium Citrate is the anticoagulant of choice for coagulation studies (PT, INR, APTT, D-Dimer).
- Sodium Fluoride is used for glucose estimation as it prevents glycolysis.
Conclusion
Understanding the different types of anticoagulants, their properties, and their applications is crucial for laboratory professionals.
Choosing the right anticoagulant ensures accurate diagnostic results and prevents sample deterioration.