Platelet Concentrate, How to Maintain Quality

The new discussion on the Blood Components group at LinkedIn on producing good quality platelet concentrates (PLT) is of very great importance. PLT is considered something of a mystery to many blood bankers and with good reason. I thought of sharing a few tips here in support of this discussion.

In the first place, there are so many methods of making PLT (see the previous post). But, that's only the beginning of the confusion. Many manufacturers the world over make blood bank centrifuges. Each manufacturer offers a number of different rotors - 4, 6, 8, and 12 place rotors are all fairly common. In each case, the way the individual centrifuge spins its rotor (the g profile) is different. So, making random donor platelets (the commonest procedure) varies widely from blood bank to blood bank. In general, though, for the first spin (platelet rich plasma or PRP method) we need to keep the g under 1000 to ensure that the g force itself does the least damage to the PLT. In each case, for a given g force, the spin time will vary. Some centrifuges have advanced braking systems, so the time to a complete stop after the spin is lessened. In other cases one has to wait patiently for the rotor to come to a complete halt.

Removing the blood bags from the centrifuge smoothly and without shake is of very great importance. Be sure to give your techs plenty of hands on training before allowing them to work with 'real' blood components. Contamination of the PLT with RBCs and with buffy-coat elements has to be minimized. Then, the technicians have to be very careful when expressing the PRP into the satelite bags not to attempt to take too much buffy-coat so as to avoid RBC contamination. Ideally a PLT of 50 to 70 mL should have less than 0.5 mL of RBC in it. The second spin yields the platelet concentrate (PLT) and platelet poor plasma. In this spin, again the g force needs to be kept as low as possible but should yield a good button of platelets which then have to be left for a short time to rest before resuspension. It's best to use a weighing device to precisely leave 50 mL (sometimes 70 mL) of plasma behind in the3 PLT bag.

For storage over 2 days, special plastic must be used which breathes and allows a high enough O2 concentration to maintain the pH in an ideal range. In situations like dengue hemorrhagic fever, or with directed donations (say for patients on chemo) where the platelets will be used within 48 hours, a lot of money can be saved for the patients by using 'ordinary' plastic double or triple bags.

At this stage, once the rest period is over, the PLT should SWIRL. this is of critical importance. Hold the PLT bag up to the light and look for the swirl. If it's not there after 2-4 hours of rest, that PLT unit should be discarded!

Some blood banks use the buffy-coat method, and here a short very hard spin is first used to produce RBC with platelets and leaving the majority of the white cells in the platelet poor plasma layer. Then a soft spin of the RBC yields the platelets in the buffy coat. This procedure, using a top and bottom bag, is common in the US. These bags are costlier and the pooling  of buffy-coats that is usually required involves the use of SCDs, but when a leukocyte filter is included you do end up with an excellent product and still less costly than when using an apheresis (cell separator) technique.

These are some basic points that I have found useful. It is a deep and fascinating subject, and I am sure that many of you may have some points to add. Comment below, or even better, submit a separate write up for publication here.

ClinLab Navigator has a short recent (2012) summary: http://www.clinlabnavigator.com/platelet-concentrates.html?letter=P

Towards targeting platelet storage lesion-related signaling pathways  Blood Transfusion 2010 June; 8(Suppl 3): s69–s72.  Peter Schubert and Dana V. Devine

Evidence-Based Platelet Transfusion Guidelines  HEMATOLOGY: January 1, 2007 vol. 2007 no. 1 172-178 Sherrill J. Slichter, MD, Director, Platelet Transfusion Research, Puget Sound Blood Center, 921 Terry Avenue, Seattle, WA 98104-1256; phone (206) 292-6541; fax (206) 292-8030; sjslichter@psbc.org

In vitro assessment of platelet storage lesion in leucoreduced random donor platelet concentrates  Blood Transfusion 2010 January; 8(1): 28–35. Amal S. Ahmed, Ola Leheta, and Soha Younes

2 videos that demo the platelet swirl:

Abstracts:

Past and future approaches to assess the quality of platelets for transfusion.  
Transfusion Medicine Review. 2007 Oct;21(4):295-306.  
Maurer-Spurej E, Chipperfield K.  emaurer@interchange.ubc.ca

Suitability of measurement of swirling as a marker of platelet shape change in concentrates
 stored for transfusion.  
Platelets. 2006 Sep;17(6):393-6.  
Mathai J, Resmi KR, Sulochana PV, Sathyabhama S, Baby Saritha G, Krishnan LK.  jaisym@sctimst.ker.nic.in