Update: "A paper published electronically in early 2003 raises some questions about the use of leukoreduced products as equivalent to CMV-negative products. The full paper may reveal things that may cause us to reconsider the above opinion. Check the latest literature for updates."
— Blood Bank Guy
In 1995, a group from Seattle published the first large study (Blood, Vol 86, No 9, 1995: pp 3598-3603) which directly compared CMV-seronegative products with filtered products for CMV prevention in bone marrow transplant recipients. The study (known most commonly as the "Bowden Study") concluded that there was no significant difference in CMV transmission between the two CMV seronegative and the filtered groups. This conclusion has been called into question somewhat in the years since, but the disagreements seem to be mostly with the wording and the scope of what was said, rather than with the basic point that leukocyte reduction reduces the risk of CMV transmission.
Part of the problem is that clinicians (and pathologists) may have a false sense of security when giving blood that is CMV-seronegative. One of the lesser quoted figures from the Bowden study is that 1% of CMV-seronegative recipients seroconverted to CMV-positive! That, to me, says that putting all of our eggs in that basket is not the greatest idea.
These discussions led to a 1997 AABB Association Bulletin (read excerpts) which concluded that if leukocyte reduction was done properly, it yielded a product which is considered equivalent to a CMV-seronegative product for preventing CMV transmission, a so-called "CMV-safe" product. It's important to recognize the part about the reduction being done properly. If someone who doesn't know how to use the filter connects it wrong, or backflushes it, or kick and stomps on it, it won't work! (big surprise)
The policy I use is simply this: If a clinician specifically requests CMV-seronegative blood, I will try to accomodate that request. However, if I have to give a CMV-seropositive unit due to supply problems, I won't hesitate to do so. Remember, though, that this is a decision that I believe must be made with the approval of the clinician. Educating your clinicians about this issue will help ease the pain of a transition here!
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