Date: Monday, June 13, 2016
Session Time: 2:30pm-4:00pm
Presentation Time: 2:54pm-3:06pm
Location: Ballroom B
This study was conducted to assess population frequency of alleles missing from single antigen bead (SAB) panels & frequency of allelic antibodies (Abs).
Methods: All positive SAB results in last 6 months were analyzed. Abs were defined as allelic (eg: A*11:01 positive, A*11:02 negative), antigenic (both A*11:01 & A*11:02 positive) or undefined (if the SAB only had one allelic bead for the antigen eg: A*23:01 positive, no other A*23 allele bead). Class II analysis was limited to DRB.
Missing HLA alleles were identified by comparing SAB panels from 2 companies (Immucor and One Lambda) to alleles present in 5 ethnic populations in the US (Source: allelefrequencies.net). Alleles with a frequency >= 0.0005 in at least one population & absent from both or at least one of the 2 panels were included.
Results: Out of 45 recipients screened with SAB, 36 had 363 Class I Abs & 21 had 70 Class II Abs. Substantial proportion of sensitized recipients have allelic Abs [47% class I (17/36) and 24% Class II (5/21)]. Majority Abs are undefined [Class I 68% (246/363), DRB 40% (28/70)]. Allelic Abs are common [25% of defined Class I (29/117) and 12% of defined DRB (5/42)].
The number of missing alleles for HLA A, B, C, DRB were 28,83,20,29 respectively. Population frequency being twice allele frequency, missing HLA A alleles are present in ~ 6% European Caucasians, 18% African Americans, 22% South/Central America Hispanics, 25% Mexicans & 54% Hawaiian in USA (frequency 0.029, 0.092, 0.11,0.125, 0.27 respectively). Similar results are present for HLA B, C, DRB
|Table 1. Combined frequency of missing alleles for different HLA molecules by population|
HLA Molecule (No. missing alleles)
|European Caucasian||African American||Mexican||Hispanic (south/central america)||Hawaiian|
Conclusion: Many HLA alleles are missing in SAB panels, each missing allele may be rare but collectively missing alleles are common, especially in the minority community. Allelic Abs are present in substantial proportion of sensitized recipients & are substantial fraction of the defined Abs. This combination of blind spots mean that in sensitized recipients a positive crossmatch with no identified donor specific Ab should not be considered a false positive till donor typing ensures that donor alleles are in the SAB panel.
CITATION INFORMATION: Kher A, Dorwal P, Kher V. Blindspots in HLA Antibody Testing: Recognition Is First Step to Nirvana. Am J Transplant. 2016;16 (suppl 3).
To cite this abstract in AMA style:Kher A, Dorwal P, Kher V. Blindspots in HLA Antibody Testing: Recognition Is First Step to Nirvana. [abstract]. Am J Transplant. 2016; 16 (suppl 3). https://atcmeetingabstracts.com/abstract/blindspots-in-hla-antibody-testing-recognition-is-first-step-to-nirvana/. Accessed April 20, 2021.
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