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Assessing the reliability of the PAK-LX HLA Class I bead in platelet transfusion compatibility testing
Haley Enten1, Abdelhamid Liacini1, Deanna Janes1
1American National Red Cross, USA.
Purpose:
PAK-LX, a Luminex-based assay for detecting platelet-specific glycoproteins and HLA class I antibodies, has shown limited reliability for HLA immunization. A prior study reported a 37% discrepancy compared to the single antigen bead (SAB) assay. The current study expands the cohort size to further investigate this discrepancy and uncover patterns that may explain the divergence.
Methods:
A total of 137 individuals from two American Red Cross Histocompatibility laboratories (Charlotte, NC and Portland, OR) were screened using both PAK-LX (Werfen, Inc) and SAB (ThermoFisher, Inc). Data included demographics, antibody positivity, discordance rates, mean fluorescence intensity (MFI), and calculated panel reactive antibody (cPRA).
Results:
SAB detected HLA class I antibodies in 73% of participants; 36% showed discordance, with 98% being PAK-LX false negatives. Mean cPRA among discordant cases was 29% (range: 2-96%). Missed antibodies had MFIs typically below 6,000 but ranged from 2,000 to 19,000.
Conclusion:
PAK-LX demonstrates reduced sensitivity for the detection of HLA class I antibodies compared with single-antigen bead (SAB) assays and may fail to identify HLA alloantibodies implicated in immune-mediated platelet transfusion refractoriness. Accordingly, PAK-LX should not be used as a standalone screening assay, and confirmatory testing with SAB is recommended when immune-mediated platelet refractoriness is suspected.
