Editing Platelet (section)

===Transfusion===
{{Main|Platelet transfusion}}

====Indications====
[[Platelet transfusion]] is most frequently used to correct unusually low platelet counts, either to prevent spontaneous bleeding (typically at counts below 10×10<sup>9</sup>/L) or in anticipation of medical procedures that necessarily involve some bleeding. For example, in patients undergoing [[surgery]], a level below 50×10<sup>9</sup>/L is associated with abnormal surgical bleeding, and [[regional anaesthetic]] procedures such as [[epidural]]s are avoided for levels below 80×10<sup>9</sup>/L.<ref name="pmid19775301">{{cite journal |vauthors=van Veen JJ, Nokes TJ, Makris M |title=The risk of spinal haematoma following neuraxial anaesthesia or lumbar puncture in thrombocytopenic individuals |journal=British Journal of Haematology |volume=148 |issue=1 |pages=15–25 |date=January 2010 |pmid=19775301 |doi=10.1111/j.1365-2141.2009.07899.x |doi-access=free}}</ref> Platelets may also be transfused when the platelet count is normal but the platelets are dysfunctional, such as when an individual is taking aspirin or [[clopidogrel]].<ref>{{cite book |veditors=Roback J, Grossman B, Harris T, Hillyer C |title=Technical Manual |edition=17th |date=2011 |publisher=AABB |location=Bethesda MD |isbn=978-1-56395-315-6 |oclc=756764486 |author=American Association of Blood Banks |page=580}}</ref> Finally, platelets may be transfused as part of a [[massive transfusion protocol]], in which the three major blood components (red blood cells, plasma, and platelets) are transfused to address severe [[hemorrhage]]. Platelet transfusion is contraindicated in [[thrombotic thrombocytopenic purpura]] (TTP), as it fuels the [[coagulopathy]].  Platelet transfusion is generally ineffective, and thus contraindicated, for prophylaxis in [[immune thrombocytopenia]] (ITP), because the transfused platelets are immediately cleared; however, it is indicated to treat bleeding.<ref>{{cite journal |vauthors=Provan D, Arnold DM, Bussel JB, Chong BH, Cooper N, Gernsheimer T, Ghanima W, Godeau B, González-López TJ, Grainger J, Hou M, Kruse C, McDonald V, Michel M, Newland AC, Pavord S, Rodeghiero F, Scully M, Tomiyama Y, Wong RS, Zaja F, Kuter DJ |title=Updated international consensus report on the investigation and management of primary immune thrombocytopenia |journal=Blood Adv |volume=3 |issue=22 |pages=3780–3817 |date=November 2019 |pmid=31770441 |pmc=6880896 |doi=10.1182/bloodadvances.2019000812 }}</ref>

====Collection====
[[File:Platelet blood bag.jpg|thumb|Platelet concentrate]]
Platelets are either isolated from collected units of whole blood and pooled to make a therapeutic dose, or collected by [[Plateletpheresis|platelet apheresis]]: blood is taken from the donor, passed through a device which removes the platelets, and the remainder is returned to the donor in a closed loop. The industry standard is for platelets to be tested for bacteria before transfusion to avoid septic reactions, which can be fatal. Recently the AABB Industry Standards for [[blood bank|Blood Banks]] and Transfusion Services (5.1.5.1) has allowed use of pathogen reduction technology as an alternative to bacterial screenings in platelets.<ref>{{cite book |author=American Association of Blood Banks |author-link=AABB |chapter=5.1.5.1 |title=Standards for Blood Banks and Transfusion Services |publisher=AABB |location=Bethesda MD |date=2003 |edition=22nd |isbn=978-1-56395-173-2 |oclc=53010679 }}</ref>

Pooled whole-blood platelets, sometimes called "random" platelets, are separated by one of two methods.<ref name="pmid1731433">{{cite journal |vauthors=Högman CF |title=New trends in the preparation and storage of platelets |journal=Transfusion |volume=32 |issue=1 |pages=3–6 |date=January 1992 |pmid=1731433 |doi=10.1046/j.1537-2995.1992.32192116428.x |doi-access=free}}</ref> In the US, a unit of whole blood is placed into a large [[centrifuge]] in what is referred to as a "soft spin". At these settings, the platelets remain suspended in the plasma. The [[platelet-rich plasma]] (PRP) is removed from the red cells, then centrifuged at a faster setting to harvest the platelets from the plasma. In other regions of the world, the unit of whole blood is centrifuged using settings that cause the platelets to become suspended in the "[[buffy coat]]" layer, which includes the platelets and the white blood cells. The "buffy coat" is isolated in a sterile bag, suspended in a small amount of red blood cells and plasma, then centrifuged again to separate the platelets and plasma from the red and white blood cells. Regardless of the initial method of preparation, multiple donations may be combined into one container using a sterile connection device to manufacture a single product with the desired therapeutic dose.

Apheresis platelets are collected using a mechanical device that draws blood from the donor and centrifuges the collected blood to separate out the platelets and other components to be collected. The remaining blood is returned to the donor. The advantage to this method is that a single donation provides at least one therapeutic dose, as opposed to the multiple donations for whole-blood platelets. This means that a recipient is exposed to fewer donors and has less risk of transfusion-transmitted disease and other complications. Sometimes a person such as a [[cancer]] patient who requires routine transfusions of platelets receives repeated donations from a specific donor to minimize risk. Pathogen reduction of platelets using for example, [[pathogen reduction using riboflavin and UV light|riboflavin and UV light treatments]] can reduce the infectious load of pathogens contained in donated blood products.<ref name="pmid15157255">{{cite journal |vauthors=Ruane PH, Edrich R, Gampp D, Keil SD, Leonard RL, Goodrich RP |title=Photochemical inactivation of selected viruses and bacteria in platelet concentrates using riboflavin and light |journal=Transfusion |volume=44 |issue=6 |pages=877–885 |date=June 2004 |pmid=15157255 |doi=10.1111/j.1537-2995.2004.03355.x |s2cid=24109912}}</ref><ref name="pmid15934989">{{cite journal |vauthors=Perez-Pujol S, Tonda R, Lozano M, Fuste B, Lopez-Vilchez I, Galan AM, Li J, Goodrich R, Escolar G |title=Effects of a new pathogen-reduction technology (Mirasol PRT) on functional aspects of platelet concentrates |journal=Transfusion |volume=45 |issue=6 |pages=911–9 |date=June 2005 |pmid=15934989 |doi=10.1111/j.1537-2995.2005.04350.x |s2cid=23169569}}</ref> Another photochemical treatment process utilizing amotosalen and UVA light has been developed for the inactivation of viruses, bacteria, parasites, and leukocytes.<ref>{{cite journal |vauthors=Prowse CV |title=Component pathogen inactivation: a critical review |journal=Vox Sanguinis |volume=104 |issue=3 |pages=183–199 |date=April 2013 |pmid=23134556 |doi=10.1111/j.1423-0410.2012.01662.x |s2cid=38392712}}</ref> In addition, apheresis platelets tend to contain fewer contaminating red blood cells because the collection method is more efficient than "soft spin" centrifugation.

====Storage====
Platelets collected by either method have a typical shelf life of five days. This results in supply shortages, as testing donations often requires up to a full day. No effective preservative solutions have been devised for platelets.

Platelets are stored under constant agitation at {{convert|20|–|24|C|F}}. Units cannot be refrigerated as this causes platelets to change shape and lose function. Storage at room temperature provides an environment where any introduced bacteria may proliferate and subsequently cause [[bacteremia]]. The United States requires products to be tested for the presence of bacterial contamination before transfusion.<ref>{{cite book |author=AABB |title=Standards for Blood Banks and Transfusion Services |publisher=AABB |location=Bethesda MD |date=2009 |edition=26th |isbn=978-1-56395-289-0 |oclc=630715051}}</ref>
[[File:Platelets collected by using apheresis.jpg|thumb|right|Platelets collected by using [[apheresis]] at an [[American Red Cross]] donation center]]

====Delivery====
Platelets do not need to belong to the same A-B-O blood group as the recipient or be cross-matched to ensure immune compatibility between donor and recipient unless they contain a significant amount of red blood cells (RBCs). The presence of RBCs imparts a reddish-orange color to the product and is usually associated with whole-blood platelets. Some sites may type platelets, but this is not critical.

Prior to issuing platelets to the recipient, they may be irradiated to prevent [[transfusion-associated graft versus host disease]] or they may be washed to remove the plasma.

The change in the recipient's platelet count after transfusion is termed the "increment" and is calculated by subtracting the pre-transfusion platelet count from the post-transfusion count. Many factors affect the increment including body size, the number of platelets transfused, and clinical features that may cause premature destruction of the transfused platelets. When recipients fail to demonstrate an adequate post-transfusion increment, this is termed [[platelet transfusion refractoriness]].

Platelets, either apheresis-derived or random-donor, can be processed through a volume reduction process. In this process, the platelets are spun in a centrifuge and plasma is removed, leaving 10 to 100 mL of platelet concentrate. Such volume-reduced platelets are normally transfused only to neonatal and pediatric patients when a large volume of plasma could overload the child's small circulatory system. The lower volume of plasma also reduces the chances of an adverse transfusion reaction to plasma proteins.<ref name="pmid16537051">{{cite journal |vauthors=Schoenfeld H, Spies C, Jakob C |title=Volume-reduced platelet concentrates |journal=Current Hematology Reports |volume=5 |issue=1 |pages=82–88 |date=March 2006 |pmid=16537051}}</ref> Volume reduced platelets have a shelf life of four hours.<ref>[http://www.cbbsweb.org/enf/2001/pltwashvol.html CBBS: Washed and volume-reduced Plateletpheresis units] {{Webarchive|url=https://web.archive.org/web/20140414063023/http://www.cbbsweb.org/enf/2001/pltwashvol.html |date=2014-04-14}}. Cbbsweb.org (2001-10-25). Retrieved on 2011-11-14.</ref>