EDTA blood tubes or purple/lavender tops as they are often called, are used for the collection of blood samples in haematology and cytology. EDTA (ethylenediaminetetraacetic acid) is an anticoagulant, that prevents blood from clotting by binding to calcium. Crucial for procedures such as blood counts and blood typing, this allows for the preservation of cell morphology.

EDTA tubes can also be used in extraction and analysis of DNA samples.

There are different forms of EDTA available, Potassium Salt (K2EDTA) and Tripotassium Salt (K3EDTA).

Once a sample has been taken, the EDTA tube should be inverted several times to ensure the anticoagulant and sample have mixed together thoroughly. The sample should then be processed immediately or stored at 2-8°C to ensure sample integrity.