When nonavailable ABO-identical platelets. What to transfuse?

Example:
Patients of group A
1st choice: AB (incompatibility major) 
2nd choice: B (incompatibility major) 

or

1st choice: O (incompatibility minor)
 

This is a controversial subject. Firstly, ABO identical is by the most effective and safest. ABO mismatched platelets are associated in randomized trials with a 2-5 fold increase in refractoriness to transfusion, with is in itself associated with early mortality.  ABO mismatched platelets in observational studies are associated with increases in febrile transfusion reactions, allergic transfusion reactions, increased bleeding and mortality.

Is a single transfusion likely to be lethal? Probably not, but the blithe use of any old ABO type for multiple transfusions is highly likely to cause morbidity and mortality.  In a pinch, when the ABO is not known or ABO identical aren't available, washed or plasma reduced group O platelets are probably safest.  If not available, group A is probably safest.  My last choice in all instances would be plasma replete group O, because there is a tiny but real risk of a fatal ABO hemolytic reaction due to the 250 ml of incompatible plasma.  Incompatible antigen is probably less risky, hence the recommendation of group A platelets. Group A plasma has anti-B, which is the least dangerous of the two isoagglutinins in every respect.  

 

Is It Time to Reconsider the Concepts of "Universal Donor" and "ABO Compatible" Transfusions?

Refaai MA, Cahill C, Masel D, Schmidt AE, Heal JM, Kirkley SA, Blumberg N.

Anesth Analg. 2018 Jun;126(6):2135-2138. doi: 10.1213/ANE.0000000000002600.