Traditionally, platelets collected by apheresis (probably better known as "single donor platelets") have been considered a better option in many cases than platelet concentrate (again, probably better known as "random platelets", or sometimes as a "six pack", because they are typically given in pools of six at a time). Here are some of the typical answers you might heard from a Blood Banker if you had asked for indications for apheresis platelets several years ago:
- Reduced exposure to potentially infectious donors
- Reduced HLA immunization (due to fewer donor exposures)
- Fewer febrile nonhemolytic reactions
- Better response in "refractory" patients (those who don't respond well to platelet transfusion)
Over the last few years, though, some of the items on this list have gradually either been disproven or have fallen into question. As we have learned more about leukocyte reduction and its effects, for example, we have realized that HLA immunization is really better prevented through removing white cells from a bag of platelets, and it really doesn't matter whether the unit is from one donor or from six donors, provided it is leukocyte reduced (This was very elegantly proven, by the way, in the so-called "TRAP" study published in the New England Journal of Medicine in 1997).
Febrile reactions, likewise, are better prevented with leukocyte reduction, in particular leukocyte reduction that occurs before the unit enters storage (more on that is in the section on prevention of febrile reactions). Finally, someone who is refractory to platelet transfusion may indeed be treated with apheresis platelets, but usually only after demonstration of the presence of either HLA-specific or platelet-specific antibodies, in which case the product of choice would be either HLA-matched or (my preference) platelet-crossmatch compatible apheresis platelets. In patients who are refractory for non-immune reasons, I see no advantage for apheresis over random platelets.
OK, so that leaves us with the first item on the list: Reducing exposures to potentially infectious donors. For my money (which is sadly a very small amount), this is really a pretty darn good reason to choose apheresis platelets! I think that one donor exposure per platelet transfusion as opposed to at least six exposures in most cases from pooled platelet concentrate is a good idea. In addition, recent studies have suggested that apheresis platelets are less likely to be contaminated with bacteria than pooled platelet concentrate. So, we are talking about a strategy that could reduce the risk of transfusion-transmitted viral infections as well as bacterial contamination.
Unfortunately, like many things we do in Transfusion, this strategy is not particularly cost-effective. An article in the September 1999 issue of Transfusion calculated the cost for this practice as being between $168,700 and $519,000 per quality-adjusted life year (Transfusion;39(Sep 99): 925-932). Even if you have no clue what a "quality-adjusted life year" is, that sounds really expensive, doesn't it? In comparison to things like HIV p24 antigen testing, though, which came out to costing millions of dollars per quality- adjusted life year, I guess this practice could be considered a bargain!
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