From the Guidelines
K2 EDTA and K3 EDTA tubes differ in their chemical form and concentration, with K2 EDTA being the preferred choice for hematology testing due to its minimal effects on cell morphology. The main difference between the two tubes lies in their EDTA formulation, where K2 EDTA is a spray-dried form applied to the tube walls, while K3 EDTA is a liquid form 1. K2 EDTA tubes typically contain 1.5-2.2 mg of EDTA per mL of blood, whereas K3 EDTA tubes contain slightly higher concentrations.
When considering the use of these tubes, it is essential to adhere to manufacturers' recommendations for blood volume filling to maintain a consistent additive-to-blood ratio among all samples, as variations in the blood-to-additive ratio can potentially influence the protein composition, such as the level of plasma t-tau 1. The anticoagulant action of both tubes works by binding calcium ions in the blood, preventing the coagulation cascade from proceeding.
Key differences between K2 EDTA and K3 EDTA tubes include:
- Chemical form: K2 EDTA is a spray-dried form, while K3 EDTA is a liquid form
- Concentration: K2 EDTA tubes contain 1.5-2.2 mg of EDTA per mL of blood, while K3 EDTA tubes contain slightly higher concentrations
- Effects on cell morphology: K2 EDTA causes less cell shrinkage and morphological changes to blood cells, making it the preferred choice for hematology testing
- Recommendation: K2 EDTA is the recommended standard by the Clinical and Laboratory Standards Institute for hematological testing, especially for complete blood counts and when cell morphology assessment is important.
From the Research
Difference between K2 EDTA and K3 EDTA Tubes
The main difference between K2 EDTA and K3 EDTA tubes lies in their anticoagulant properties and effects on blood samples.
- K2 EDTA tubes contain a lower concentration of EDTA, typically 1.8-2.2 mg/mL, whereas K3 EDTA tubes contain a higher concentration, usually 3.6-4.4 mg/mL 2.
- The choice of anticoagulant can influence the results of hematological tests, particularly in less-than-optimal conditions, such as high anticoagulant concentrations or delayed measurement 2, 3.
- Significant differences have been found in certain parameters, including neutrophils, mean platelet volume, monocytes, and red blood cell distribution width (RDW), when comparing K2 EDTA and K3 EDTA tubes 3.
- However, for some tests, such as HbA1c measurement, there is no statistically significant difference between K2 EDTA and K3 EDTA tubes 4.
- The stability and reproducibility of blood samples in K2 EDTA and K3 EDTA tubes can also vary, with some studies showing significant differences in certain parameters over time 3.
- Haemolysis can also affect the results of complete blood count (CBC) tests, with gross haemolysis leading to unreliable results 5.
- Other anticoagulants, such as EDTA plus citrate-theophylline-adenosine-dipyridamole (EDTA-CTAD), have been investigated for their potential to inhibit platelet activation and improve the accuracy of flow cytometric assessments of platelet and neutrophil activation 6.