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#79
AN IRONY OF HLA PHENOTYPING: A CASE STUDY.
Zahra Mehdizadeh Kashi, ph.D., Jason Alcorn, Suzie Pendergrass, Allan Karsk and David Baumgarten. Portland OR, USA, American Red Cross, 97227, Clinical Servcies, Tissue Typing Laboratory.

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A sample was submitted for molecular HLA Class I and Class II phenotyping. We performed a generic resolution SSP typing using One Lambda kit to obtain the HLA type as follows: A*2, A*11, B*15, B*46, DRβ1*11, DRβ1*12, DRβ3, DQβ1*03. Three months later, another sample from this patient was submitted with a request for serologic HLA Class I and Class II typing. Using the immunomagnetic Dynal bead technology, we obtained the following HLA type: A2, A11, B62(BW6), DR5, DR52, DQ3. The serologic method did not pick up the second HLA-B antigen due to the overlapping antisera used. Although, three commercial trays were used, this common limitation in serologic testing led to a blank locus since all of the B46 antigens were masked by B62. A close study of the HLA types obtained by two methods for both Class I and Class II typing in this case and several others reveals an irony that induced us to submit this abstract. Although the molecular technique offers a more superior resolution, both serologic and molecular methods share some weaknesses. In this case, the serology resulted in a more defined HLA-B antigen (B62) compared to the molecular technique whereas it led to a "mistype" for the second HLA-B antigen (B blank). Ironically, serologic HLA-DR antigens were reported as DR5, once again due to the overlapping antisera for HLA-DR11 and HLA-DR12 on two commercial trays. These observations reiterate that greater challenge of serological typing remains associated with the less common antigens often exhibited in minorities. In conclusion, to improve the accuracy of tissue typing, we may consider molecular technique the method of choice for different ethnic groups as molecular typing uncovers HLA "mistyping" predominantly in such individuals.