3. To avoid contaminating the sample with tissue thromboplastin or heparin, follow the guidelines below. These substances may alter results.
- The venipuncture must be clean, with no trauma.
- Hemolyzed samples are not acceptable.
- The first 5 mL of blood drawn from a patient should not be used for coagulation testing.
- If drawn through an indwelling catheter, flush with 5 mL of saline and discard the first 5 mL of blood collected before collecting the specimen for coagulation testing. Blood should not be collected from heparinized lines.
4. Mix the sample gently by inverting the tube gently at least but not more than four times immediately after filling.
5. Process the sample as soon as possible (within 60 minutes). Do not store whole blood samples refrigerated prior to processing. Spin down the specimen at a speed and time required to produce platelet poor plasma (<5,000 - 10,000/uL). This can be accomplished by centrifuging at 1500 x g for 15 minutes.
6. Preparing samples for transport:
- Transfer plasma into a plastic tube using a plastic Pasteur pipette. Do not use glass tubes or glass Pasteur pipettes as glass can activate the clotting cascade.
- Label each tube “plasma.” Submit a plasma aliquot for each and every coagulation assay requested (one tube for each test). If possible, submit one additional plasma aliquot for repeat and/or test additions.
- If you are requesting other tests that require serum, please label these tubes as “serum”.
7. Ship samples for testing on dry ice. Samples must remain frozen in transit.
8. We highly recommend quick-freezing the sample to keep coagulation factors intact. This can be achieved by one of the following methods:
- Freeze with liquid nitrogen.
- Freeze in a mixture of dry ice and methanol.
- Freeze in a -70°C freezer.