Citrated Blue Top Tube (BTT) must be drawn to the fill line. Completely invert tube three or four times to mix. Do Not Shake. Centrifuge tube at 3000 rpm for 10 minutes or Stat Spin for 3 minutes at 8500 rpm with the brake OFF as soon as possible after collection. Perform testing within 4 hours of sample collection or transfer plasma (avoiding platelet contamination) to polypropylene tube with plastic pipette for storage within two hours of collection.
If sending to another testing location: Send one frozen aliquot (1 mL) labeled with both APTT and Protime-INR labels if both APTT and Protime-INR ordered.