Special Instructions

Patient should be off warfarin (Coumadin) for at least 2 weeks, or on a stable dose of warfarin for at least 2 weeks before drawing sample.

Specimen cannot be hemolyzed or clotted.

To obtain a coagulation plasma sample, centrifuge the capped specimen tube at a speed and time required to consistently produce platelet-poor plasma (platelet count < 10,000/uL). The centrifugal speed and duration to accomplish this must be established in the individual laboratory. Our laboratories use centrifuges at 3,000 to 4,000 rpm for ten minutes or higher speed and shorter duration centrifuges. When removing plasma to send for coagulation testing, it is important NOT to go all the way down to the cells. Leave a minimum 1/4 inch of plasma sitting on cells. This layer contains the platelets which were separated from the plasma during spinning. The platelets interfere with coagulation testing so we leave this layer undisturbed.