Red blood cell transfusion in patients with anti-Yt^a

Yt^a is a high frequency red blood cell (RBC) antigen, present in 99.7% of studied populations. It is extremely immunogenic, and when anti-Yt^a is present, provision of Yt(a-) blood is often challenging. The objectives of our study were to assess the incidence and severity of acute hemolytic transfusion reactions to Yt(a+) donor RBCs in recipients with preformed anti-Yt^a and to identify any patient factors associated with severe hemolytic reactions.

Patients with anti-Yt^a identified by the Red Cell Reference Laboratories of the Australian Red Cross Lifeblood over the past 20 years were included. Their transfusion records were collected via the referring laboratory to ascertain if any patients received RBC transfusion and if there was any evidence of transfusion reactions.

Fifty-two patients with anti-Yt^a were identified; only 12 were confirmed to have received a RBC transfusion. Nine received Yt(a+) or untyped allogeneic RBCs, including four patients who received a total of 16 indirect antiglobulin test (IAT) crossmatch incompatible, likely Yt(a+) RBCs. None of the nine patients had documented acute hemolytic reactions.

There are limited published data describing the clinical significance of anti-Yt^a . Based on our data, it appears that transfusing patients with anti-Yt^a using incompatible crossmatched RBCs does not pose a significant risk of an acute hemolytic transfusion reaction when the antibody reaction strength is weak ≤2+ (0-4) by IAT crossmatch. For strong examples of the antibody, in the absence of other assay data, such as the monocyte monolayer assay, Yt(a-) blood should continue to be sourced where possible.