Thread by @BukuHaematology

1/ When transfusing platelets, the mantra of;

'Why use two when one will do?'

Is supported by data from the PLADO study + others (see refs) which show that giving more than a standard dose of platelets (1 pool/unit* in an adult) did not ⬇️ bleeding incidence

2/ Each platelet exposure has (uncommon but significant) risks of allergic reaction, virus transmission and...

Each exposure to platelets is also another potential exposure to HLA antigens which the recipient does not have

3/ This may not have a big impact for many patients but for those awaiting transplants (haem or solid organ @BukuRenal) it increases the chance of graft rejection.

Why does this happen?

4/ Standard platelet transfusion are not HLA-matched, and this is fine because most of us will never need platelets, and if we do, it is often a 'one-off' during critical illness

Even for haematology patients who receive many platelets, HLA sensistization is not often a problem

5/ With each platelet transfusion however the chance increases of the immune system becoming 'aware' of these non-self antigens

5/ When this occurs, antibodies can form against those HLA antigens. Again, for many of us that is not an issue as our body will never 'see' those antigens again.

If however the patient needs a solid organ transplant for example, there is a risk of rejection of that organ...

6/ ...when it is introduced to the body
➡️ acute rejection.

In bone marrow transplants, antibodies against HLA on the donated bone marrow stem cells can prevent the stem cells engrafting/'moving in' to the recipient marrow space/their new home

7/ SO platelet transfusions can be critical for patients w. low platelet counts and bleeding/procedure but are often given when not indicated. And please only give one unit & review, as evidence says that 2 pools do not help more than 1 ➕ is an unnecessary blood product exposure

8/ *FACT: Platelets are prescribed as a 'pool because it us a single dose made from multiple donors. Single donor units aka apheresed units are available and reduce HLA exposure for those at risk

Ref; Dose of Prophylactic Platelet Transfusions and Prevention of Hemorrhage | NEJM nejm.org/doi/full/10.10…

Ref; @NHSBT presentation with slide summarising the evidence of low dose vs high dose olatelst transfusion transfusionguidelines.org/document-libra… #MedTwitter #MedEd #FOAMed