Human immunology · 2026
Assessing the reliability of the PAK-LX HLA Class I bead in platelet transfusion compatibility testing.
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Enten Haley, Liacini Abdelhamid, Janes Deanna, Stedem Robin, Gaule Logan, Berka Noureddine
Аннотация
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.
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.