(P-TS-58) How Low Do You Go When Titering O Platelets

Our institution screens all group O platelets in our inventory for high titer anti-A, defined by a titer of ≥1:200. We track the prevalence of high titer anti-A for these platelets as well as their final disposition. The goal of this project was to evaluate a new cutoff, defining a high titer as ≥1:100 and the effect it would have on our platelet inventory.

Study

Design/Methods:

Plasma from each platelet product or donor sample is currently diluted 1:200 with saline. The diluted plasma is tested against A1 commercial RBCs (BioRad) at immediate spin tube methodology. Any agglutination is interpreted as a positive high titer. Group O platelets meeting this criterion are labeled with instructions to be transfused only to group O patients. We repeated this testing on 224 group O platelets to compare the positive reaction rate using a saline dilution of 1:100 to the current 1:200.

Results/Findings:

Since implementation, we have tested 22,013 group O platelets with a positive reaction rate of 3.58% at 1:200 dilution. Of the 224 group O platelets tested at both 1:200 and 1:100, the 1:200 cohort had a positive reaction rate of 3.57% and the 1:100 cohort had a positive reaction rate of 16.52%.

Conclusions:

The results of this project show that a 1:100 cutoff significantly decreases the number of O platelets in our inventory that can be transfused to group A or AB patients. From these results, our institution has decided to continue our screening process with 1:200 as the cutoff, as 1:100 would be too restrictive. However, other factors currently under investigation include hemolytic transfusion reactions due to anti-A, and overall O platelet discard rates. Our current process will be re-assessed once all of these considerations can be evaluated in parallel.