Background/Case Studies: Platelet transfusion refractoriness (PTR), defined as failure to achieve an appropriate platelet (plt) count increment following 2+ consecutive plt transfusions, represents a significant challenge. Most PTR cases (~80%) have non-immune etiologies; ~20% have an immune etiology primarily caused by antibodies (Ab) targeting human leukocyte antigens (HLA), leading to rapid clearance of transfused platelets.
Our management of immune-mediated PTR (iPTR) involves performing a plt crossmatch (XM) using patient serum and random plt units to find compatible units or ordering an HLA antibody specificity panel (ASP) and utilizing the results to guide a search for antigen-negative units from a community blood center. Plt XM offers several advantages, including the ability to quickly identify compatible units from existing inventory without requiring lengthy and complex laboratory tests (HLA antibody panel) or HLA-typed donors, potentially reducing the time to provide compatible platelets. This method may be particularly valuable for patients with urgent transfusion needs or those with few Ab or Ab to low-frequency HLA antigens (low calculated Panel Reactive Antibody (cPRA)). Our retrospective observational study aims to assess differences in turnaround time (TAT) at our institution for finding compatible plt units between these two approaches.
Study
Design/Methods: Plt XM was available Mar 2022-Dec 2023. Of 133 patients with an order for a plt refractory workup, 40 hospitalized patients were randomly selected for this pilot study. Patients with splenomegaly, disseminated intravascular coagulation, sepsis, or if they required a massive transfusion protocol were excluded.
HLA ASP test performed with LABScreen Single Antigen HLA Class I assay (One Lambda, Canoga Park, CA). Plt XM utilized Capture-P assay (Immucor, Norcross GA); 6 plt XM were performed per test.
9 patients (69.2%) had HLA ASP ordered; average TAT of the ASP was 3.7 days. 3 patients had a negative ASP. Of those patients with a positive ASP (66.7%; cPRA range 15-96%), HLA antigen-negative platelets were obtained from a community blood center within an average of 4 days from the time of ASP order.
11 patients (84.6%) had plt XM performed; average TAT to complete plt XM was 1.4 days. 8 patients had both plt XM and HLA ASP performed. XM-compatible platelets were available within an average of 1.6 days from the time of XM order.
Conclusions: Plt XM provides a faster method for identifying appropriate and accessible plt units compared to using HLA ASP results to guide product search. This method may also identify iPTR due to anti-HPA Ab in addition to anti-HLA Ab. As algorithms for PTR continue to be optimized, this study reinforces the use of plt XM as a first-line method in managing patients with iPTR, decreasing the time needed to provide a compatible plt unit.
