P055 To be a DSA or not to be a DSA, we need to know!

Abstract

Aim The accuracy of HLA antibody testing is very important for entering UNOS Unacceptable donor antigens, evaluating organ offers by virtual and prospective crossmatch, and evaluating donor specific antibodies (DSAs) pre and post transplant. It is known that Single Antigen Beads (SAB) often have problems with false positive reactions, when the manufacturing process results in 3–5% denatured HLA determinants on every bead, exposing cryptic, non HLA antigens. This case study demonstrates that SAB false positive HLA antibodies can often be ruled out or verified by using additional tests and analyses, including FlowPRA Screen and LSPRA (phenotype bead) assays and epitope and donor HLA allele analysis, which will reduce the risk of denying lifesaving organ transplants based on false positive HLA antibodies. Methods Deceased donor pronased mononuclear cells from blood, were Flow crossmatched against three sera from a 64% CPRA patient. The results were T cell Negative on all three sera, B cell low positive on one of the sera. By SAB the sera had three potential weak DSAs (B62/2,100 MFI, DRB3*02:02/1,000 MFI, DPB1*01:01/A1*01:03/2,500 MFI, and DPB1*01:01/A1*02:01/1,000 MFI), LSPRA assay, crossmatch results, and epitope and donor alleles analysis, were used to rule out or confirm the potential DSAs. Results The three potential DSAs were ruled out, see the table below. The B cell Low Positive in serum 1 did not make sense, the potential DSAs were stronger in serum 3, the reactivity was nonspecific, which had been observed before. Download high-res image (204KB) Download full-size image Conclusions It is unacceptable that alone, the SAB assay false positive DSAs will deny patients lifesaving organ transplants, when there are tests and analysis methods which can often detect and rule out these antibodies. The SAB assay is a very important test, but unless other testing platforms, like Phenotype beads and FlowPRA screen, are used to identify the false positive antibodies, the SAB assay will lose organ offers for our patients or trigger unnecessary DSA treatments post transplant. S.S. Geier: 2. Consultant; Company/Organization; LABSNE Clinical Consulting Director. 7. Other (Identify); Company/Organization; UNOS Histocompatibility Committee and MPSC ad.