PLASMA PREPARATION TIPS
GUIDLINES FOR COLLECTION AND PREPARATION OF PLATELET POOR PLASMA
Lifespan Technologies’ assays are sensitive to methods of sample collection and processing. Test results are a direct reflection of sample integrity. Improper collection and processing of plasma may result in decreased assay sensitivity. We recommend the following collection and processing guidelines for optimal results
Collection Procedure
1) Anticoagulant
3.2% sodium citrate is the anticoagulant of choice. These tubes have light blue tops. We have tested EDTA (purple top tubes) as an anticoagulant; however, EDTA degrades the assay sensitivity and is therefore not recommended.
2) Collection
Venipuncture is the preferred method of collection. If a 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. 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. Invert filled tubes several times to ensure adequate mixing with the anticoagulant.
If samples are being collected from a catheter, ensure that it is maintained with saline only (no heparin). Discard the first 5-10mL of blood collected.
Our Experience with Plasma
- Whether using human or animal plasma, the centrifugation steps are very important. One needs fresh, platelet-free, or at least platelet-poor plasma.
- We realize that it is extremely difficult to follow all of the guidelines when using animal plasma, and nearly impossible with rodent plasma. We suggest you follow as many of the guidelines as possible.
- Use sodium citrate (light blue top tubes). Citrate is the most common anticoagulent for work in coagulation science. We have used EDTA as anticoagulent, but EDTA degrades the assay sensitivity and is therefore not recommended.
- Try to get the blood into the centrifuge immediately after drawing and to remove the plasma immediately after the centrifugation.
- It is important to use aspiration to remove the plasma, and to avoid disturbing the ‘buffy coat’, the white cells on top of the red cells.
- Once the plasma is platelet-free it is best to immediately store it at -70˚ or -80˚C. We have stored our standards for years in this fashion and have not seen a problem with degradation.
- Plasma should not be thawed multiple times. Freeze only once. It is best to aliquot and freeze the appropriate amounts of plasma you will use for each days testing.
Post-Collection Steps - Preparation of Platelet Poor Plasma
It is important that the following sample processing procedure be followed exactly.
- Within 30 minutes of collection, centrifuge capped citrate tube(s) for 10 minutes at an RCF (relative centrifugal force) of 2000g.
- Using a plastic transfer pipet, remove the top 3/4 of plasma, being careful not to disturb the buffy coat. Place this plasma in a separate plastic centrifuge tube with cap.
- Centrifuge the plasma, now in the plastic centrifuge tube, for another 10 minutes at 2000g (3000g is better if your centrifuge will allow.)
- Using a plastic transfer pipet, remove the top 3/4 of plasma from Step 3 into plastic tubes. Do not disturb the plasma in the bottom of the spun tube, where any residual cells will be.
- Freeze plasma immediately. Samples should be frozen within 1 hour of collection.