Snehil Kumar1, Sam Arul Doss2, S Stephen2, M Pratheeba2, L Jeyaseelan3, Dolly Daniel4. 1. Department of Transfusion Medicine and Immunohaematology, Christian Medical College, Vellore 632004, Tamil Nadu, India. Electronic address: snehil25@cmcvellore.ac.in. 2. Department of Transfusion Medicine and Immunohaematology, Christian Medical College, Vellore 632004, Tamil Nadu, India. 3. Department of Biostatistics, Christian Medical College, Vellore 632004, Tamil Nadu, India. 4. Department of Transfusion Medicine and Immunohaematology, Christian Medical College, Vellore 632004, Tamil Nadu, India. Electronic address: dollyd@cmcvellore.ac.in.
Abstract
INTRODUCTION: Detection of donor specific antibodies (DSA) is critical in both solid organ and mismatched haematopoietic stem cell transplants. The single antigen bead assay (SAB) is widely used as a virtual crossmatch in these settings. However, HLA allele variation across ethnicities and differing genetic backgrounds is a well-known and acknowledged fact and representation of alleles prevalent in a population is key while using a virtual crossmatch as a sole decision making tool. Against this background, this study was performed to assess the feasibility of using the SAB as a single tool to identify DSA in our population. MATERIALS AND METHODS: The HLA alleles identified in the study population were analysed to assess their representation on SAB panels from two different vendors. RESULTS: The study population comprised of a total of 966 subjects for whom 6 loci high resolution HLA typing was done. A total of 241 different alleles were assigned in the population. Among the 241 alleles identified in our study population, 48.55% (n = 117) alleles were represented in the SAB A panel and 48.13% (n = 116) represented in the SAB B panel. Unrepresented alleles were 51.45% (n = 124) in panel A and 51.87% (n = 125) in panel B. All the twelve alleles were represented for 16.05% (n = 155) and 16.25% (n = 157) of study population in panel A and in panel B respectively. The remaining individuals (83.95%, (n = 811) in panel A and 83.75%, (n = 809) in panel B) had at least one allele unrepresented. CONCLUSION: Our study addresses an important limitation in utilizing the SAB as a single tool to identify DSA, owing to non-representation of locally prevalent / unique alleles in our population. More than 50% of alleles were unrepresented in both the SAB assays we studied, which included alleles from both Class I and Class II. We recommend therefore that, until a comprehensive coverage of alleles is provided, or epitope matching becomes robust, that the SAB be combined with a physical crossmatch when mismatched alleles are not represented.
INTRODUCTION: Detection of donor specific antibodies (DSA) is critical in both solid organ and mismatched haematopoietic stem cell transplants. The single antigen bead assay (SAB) is widely used as a virtual crossmatch in these settings. However, HLA allele variation across ethnicities and differing genetic backgrounds is a well-known and acknowledged fact and representation of alleles prevalent in a population is key while using a virtual crossmatch as a sole decision making tool. Against this background, this study was performed to assess the feasibility of using the SAB as a single tool to identify DSA in our population. MATERIALS AND METHODS: The HLA alleles identified in the study population were analysed to assess their representation on SAB panels from two different vendors. RESULTS: The study population comprised of a total of 966 subjects for whom 6 loci high resolution HLA typing was done. A total of 241 different alleles were assigned in the population. Among the 241 alleles identified in our study population, 48.55% (n = 117) alleles were represented in the SAB A panel and 48.13% (n = 116) represented in the SAB B panel. Unrepresented alleles were 51.45% (n = 124) in panel A and 51.87% (n = 125) in panel B. All the twelve alleles were represented for 16.05% (n = 155) and 16.25% (n = 157) of study population in panel A and in panel B respectively. The remaining individuals (83.95%, (n = 811) in panel A and 83.75%, (n = 809) in panel B) had at least one allele unrepresented. CONCLUSION: Our study addresses an important limitation in utilizing the SAB as a single tool to identify DSA, owing to non-representation of locally prevalent / unique alleles in our population. More than 50% of alleles were unrepresented in both the SAB assays we studied, which included alleles from both Class I and Class II. We recommend therefore that, until a comprehensive coverage of alleles is provided, or epitope matching becomes robust, that the SAB be combined with a physical crossmatch when mismatched alleles are not represented.
Authors: S Peacock; D Briggs; M Barnardo; R Battle; P Brookes; C Callaghan; B Clark; C Collins; S Day; N Diaz Burlinson; P Dunn; R Fernando; S Fuggle; A Harmer; D Kallon; D Keegan; T Key; E Lawson; S Lloyd; J Martin; J McCaughan; D Middleton; F Partheniou; A Poles; T Rees; D Sage; E Santos-Nunez; O Shaw; M Willicombe; J Worthington Journal: Int J Immunogenet Date: 2021-09-23 Impact factor: 2.385