The reason why there are differing opinions on platelets and ABO is because platelets don’t normally have ABO antigens. It’s the plasma fraction most worry about (so a type O donor will have anti-A and anti-B, type B will have anti-A, etc). The way I learned it and one hospital I worked at determined it was type specific first, AB next (as they are the “universal plasma donor”), and type O is given lowest priority to A, B, or AB patients (and anti-A and anti-B should be titered from those units in any case). In theory, a platelet unit from any ABO type can be donated to a recipient of any ABO provided the titers of the ABO antibody which could cause red cell destruction in the recipient aren’t high in the donor unit. Of course when it comes to platelets, there are other factors than ABO to consider.

Nowadays I work in an immunohematology reference laboratory and most of my platelet work is in serological crossmatching or HLA matching. I still use the same principles and since the IRL also serves as a donation center, the goal is to try to turn every AB donor into a plasma/platelet donor and all O donors into red cell donors. Type O platelets are still useful as most of the population is type O anyhow, but if I can’t get a type specific donor who is compatible (also depends on CMV status) I will go back to the plasma ABO compatibility chart for reference when selecting units.

Long story short, I don’t think you can go wrong by using the plasma ABO compatibility rules for platelets although you should remember that in theory ABO is not relevant for the platelets themselves as they don’t express ABO antigens. It’s the ABO antibodies in the plasma fraction which are usually relevant for this case.

BTW- Rh positive and negative isn’t really relevant in this case because RhD is not expressed on platelets (the Rh system is expressed on red cells). Platelets from an Rh positive donor will not have the D antigen and donors who are Rh negative with an anti-D are screened out in donor testing.