K2-EDTA or K3-EDTA: Which anticoagulant to choose for hematology testing?
Frequently asked question from our partners is:
“Which collection tube should we use with Diatron’s hematology analyzers, K2-EDTA or K3-EDTA?”
Both EDTA salts (K2-EDTA and K3-EDTA ) inhibit the coagulation of the blood specimen by binding Calcium (Ca2+), thus preserving the blood cells for test analyses. The K2-EDTA and K3-EDTA additives preserve erythrocytes, leucocytes and thrombocytes up to 24 hours, depending of the storage conditions of the sampling tube.
In a publication dated 19931, the International Council for Standardization in Hematology (ICSH) generally recommends the use of K2-EDTA. Potassium salts have the advantage of being easily soluble in the blood when present in dry form in the collection tube.
So why using K2-EDTA rather than K3-EDTA?
Potassium salts cause a shrinkage of red blood cells. The higher the concentration of Potassium salts, the greater the shrinkage of red blood cells, causing, among other things, a reduction in Mean Cell Volume, observed with K3-EDTA. Moreover, its liquid form use generates lower values of the measured parameters (Red Blood Cell, White Blood Cell, Hemoglobin) by dilution effect.
In conclusion, while both are effective, K2-EDTA is often preferred in modern hematology due to its minimal dilution impact and stability with newer analyzers. However, some facilities still use K3-EDTA based on specific protocol or cost considerations.
1 Recommendations of the international council for standardization in hematology for ethylenediaminetetraacetic acid anticoagulation of blood for blood cell counting and sizing, October 1993 American Journal of Clinical Pathology 100(4):371-372