Thread by @TransfusionWM

Today I did an online tutorial with the West Midlands #haemSpRs. It was good to do some teaching after a bit of a hiatus! We've always done online tutorials on Whatsapp but videoconferencing was a win. #Covidsilverlinings

Follow this thread for a #blooducation #tweetorial

We talked about platelet refractoriness and its definition. Strictly this is by a recovery value or corrected count increment based on patient size and volume of platelets transfused, but practically we use the rise in platelet count measured within 24h of transfusion.

This should be checked twice, with ABO matched plt which are =< 3 days old. What increase in platelet count is deemed insufficient?

A platelet count rising by <10 following transfusion is insufficient and merits further investigation.

Refractoriness can be immune or non immune. It is important to consider non immune causes before looking for immune causes although in reality most non immune causes are not correctable in the heat of the moment!

What causes of non immune refractoriness can you think of…?

Sepsis, bleeding, drugs (including amphotericin and piperacillin) and splenomegaly are all causes of non immune refractoriness.

Immune causes are HLA, HPA and ABO antibodies (ABO antigens are present on platelets), and autoantibodies. HLA antibodies are frequently found in multiparous women (and transfused patients) and do not always cause refractoriness.

If HLA antibodies are found and the patient is refractory to random platelets, HLA *selected* platelets should be given. NB these are not always completely *matched*.

For platelet selection, HLA-A and -B antigens are matched as much as possible. HLA-C antigens are weakly expressed on platelets and are thought not to have a significant role in refractoriness.

If HLA abs are not found, HPA abs are tested for. In patients with high probability of immune refractoriness and no antibodies demonstrated, a trial of HLA selected platelets can still prove clinically effective…

… but if not effective, review the request for HLA selected and consider reverting to random (ABO matched) platelets (esp where non immune causes are likely).

Platelet matching is graded A-C, with A being both HLA-A and both HLA-B antigens matched. Knowledge of about cross-reactive groups (CREGS) of antigens is allowing “smarter” platelet matching in patients where a grade A match cannot be found.

Platelet increments measured at 15-60 min post transfusion are vital for establishing efficacy and will inform donor selection for future transfusions.

Typically HLA platelets will be available the day after requesting, but if required more urgently please d/w NHSBT Hospital Services as same day provision is often possible where there is clinical need.

And remember, HLA platelets must be irradiated!

Thanks for following this far!

More information on platelet refractoriness is available in this excellent review by @AndelLestcourt and @SimonStanworth

onlinelibrary.wiley.com/doi/full/10.11…

And the NHSBT clinical guideline can be found here hospital.blood.co.uk/clinical-guide…