HLA-Matched Platelet policy

[Mabel Adams]

I am revising our procedure for HLA-Matched platelets and reviewing literature so we can have an evidence-based policy.  If you are a hospital without its own HLA lab, what approach do you take?  Do you start with HLA antibody testing and give units compatible with the antibodies found and only HLA type the patient if they have a high percent reactive (PRA) or do you always start with HLA typing the patient?  When do you order HPA antibody testing?  Do you know of evidence to support your approach?  It might also be helpful to know if you are across town from your HLA Lab and blood supplier or more remote.  Thanks for any input.

[Neil Blumberg]

To much make refractoriness a non-problem, one needs to administer leukoreduced and ABO identical blood components. In our hands, that pretty much abrogates the problem entirely.  Almost all of our 3-5 refractory patients per year (out of hundreds) are treated elsewhere first with non-ABO identical components which randomized trial data show increases the rate of HLA alloimmunization.  One cannot control what other people do, obviously.

So when a patient is clinically refractory, we will HLA type them, try to characterize the antibodies (PRA) and either give HLA matched,  or avoid specificities when that is feasible.  Either works about as well (probably 70-80% of the time).  If those HLA identical platelets are ABO non-identical, they will perform about as badly as non-HLA matched.  Thus we try to avoid that or remove incompatible plasma from HLA-matched, plasma incompatible platelets (we wash).

It's a good idea to have HPA antibody testing, although not essential,  as about 1-2% of refractory patients have HPA antibodies (thus it's rare, but not zero) and this test will also indicate if you have one of the patients who actually have ITP (about 50% of ITP patients have anti-platelet antibodies).  There are fairly simple kits available to screen for both HPA and HLA antibodies,  although they don't allow for specificity determination.