Preparation of Platelet Poor Plasma for Coagulation Testing

For Any Test Requiring Frozen Plasma From a Light Blue Top Tube

Coagulation assays are extremely sensitive to methods of sample collection and processing. Test results are a direct reflection of sample integrity. It is the client’s responsibility to adhere strictly to processing guidelines.
 

Anticoagulant

3.2% sodium citrate is the anticoagulant of choice for all coagulation tests that require plasma. These tubes have light blue tops.
 

Order of Draw

Light blue top (citrate) tubes should be collected before other tubes. Draw approximately 2 mL of blood into a citrate tube (for discard) and then continue to draw the appropriate number of properly filled citrate tubes.
 

Collection

Venipuncture is the preferred method of collection. If good blood flow cannot be obtained, a repeat venipuncture is recommended. Use of a size 21-gauge needle (size 23 minimum) will help avoid hemolysis. Samples may be collected from catheters maintained with saline only (no heparin). Discard the first 5-10mL of blood collected.
 

Acceptable Fill Volumes

Each size of tube must be properly filled, as the ratio of blood to anticoagulant is critical to testing. Patients with high hematocrits (>55%) should be collected into special hematocrit-adjusted tubes (available upon request).
 

Preparation of Platelet Poor Plasma

It is critical that the following specimen processing procedure be followed exactly.
 

1. Within 3 hours of collection, centrifuge capped citrate tube(s) for 10 minutes at an RCF (relative centrifugal force) of 1500-2000g. For the heparin tests (order codes HEPXA, UFHEP and LMWHEP), tubes should be centrifuged within 1 hour of collection.
 
2. Using a plastic transfer pipet, remove the top 3/4 of plasma. Place this plasma in a plastic centrifuge tube with cap.

3. Using a wooden applicator stick, check the cells remaining in the blue top tube(s) for a clot. Do not submit plasma from tubes in which a clot was detected.

4. Centrifuge the plasma (in the plastic centrifuge tube from Step 2 above) for another 10 minutes at 1500-2000g.

5. Using a plastic transfer pipet, remove the top 3/4 of plasma from Step 4 into plastic tubes (at least 1/2 mL of plasma per aliquot). Do not disturb the plasma in the bottom of the spun tube, where any residual platelets will be.

6. Aliquots with visible red cells or hemolysis (pink plasma) are not acceptable.

7. If only one test is ordered, submit two aliquots. One citrate tube will usually yield two aliquots of at least 0.5 ml each.

8. Label tubes with sample type (citrate plasma) and date and time of collection.

9. Freeze plasma immediately. Samples for most assays should be frozen within 4 hours of collection (see individual test requirements for specifics).

Samples must remain frozen during transport. Use dry ice to guarantee that specimens will not thaw.

TriCore recommends saving at least 1 of the original light blue top tubes for 1 week in your refrigerator in case factor mutation testing is desired.
 

For more information, contact TriCore’s Special Coagulation Department at 505-938-8844 or 800-245-3296 Ext. 8844.

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