Salts of EDTA (ethylenediaminetetraacetic acid) are used for the anticoagulation of whole blood for haematological examinations, as the cellular components of the blood are particularly well preserved by EDTA. It acts as an anticoagulant by forming complexes with metal ions such as calcium2+ and removing it from the enzymes of the coagulation cascade. Anticoagulation with EDTA is irreversible.
The EDTA concentration in BD Vacutainer® tubes is 1.8 mg per mL of whole blood at the correct fill level, as recommended by ICSH (International Council Society of Haematology) and CLSI (Clinical and Laboratory Standards Institute). These institutions recommend the dipotassium salt of EDTA (K2 EDTA) for haematological investigations. K2 EDTA is used in BD Vacutainer® tubes made of plastic in spray-dried form. K3 EDTA is the less suitable EDTA salt for anticoagulation of samples for haematology, as it can have a more pronounced effect on cells (e.g. shrinkage of red blood cells) with increasing EDTA concentration (for example, with incompletely filled tubes). K3 EDTA is used in BD Vacutainer® tubes made of glass in liquid form, in BD Vacutainer® tubes made of plastic in spray-dried form.
Crucial for optimal sample quality in EDTA whole blood tubes for haematology is that the EDTA dissolves quickly in the blood, thus minimising the formation of microclots. This is supported by the special process by which K2 EDTA is distributed and spray-dried on the inner tube wall of BD Vacutainer® tubes.
Swirling the tubes Proper mixing (8-10 x) of the EDTA tubes immediately after blood collection is particularly important to avoid microclots
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