Vacuum blood collection tubes for testing the haemostasis system contain EDTA salts to block the clotting cascade by way of binding calcium ions to ensure the stability of red cells, white cells and platelets in the blood sample for up to 24 hours. It is recommended to make a blood smear within 4 hours of the sample being collected. Transparent labels ensure: • total visual control of sample state • optimal solution for ESR analysers making optical measurements in automated mode • easier automated control while sorting and dosing samples in analysers