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P047 Stability of anti-A2 blood group subtype titers among blood group B candidates
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P046
Abstracts / Human Immunology 78 (2017) 51–254
HLA CLASS II EPLET MISMATCH PREDICTS DE NOVO DSA FORMATION AT 3 AND 12 MONTHS POST LUNG TRANSPLANT Duncan Walton a, Steven Hiho a, Linda Cantwell a, Joseph Ta a, Monika Loskot b, Tracy Phan b, Bronwyn Levvey b, Greg Snell b, Miranda Paraskeva b, Glen Westall b. aAustralian Red Cross Blood Service, West Melbourne, Australia; bThe Alfred Hospital, Melbourne, Australia. Aim: The aims of this prospective study were: 1) investigate a cohort of LTx recipients for the presence and clinical associations anti-HLA antibodies 2) Examine association between HLA eplet mismatch and HLA de novo antibody formation. Methods: From Jul 2014-Aug 2015, 49 patients were enrolled at time of listing for LTx, and blood samples obtained pre-transplant and at 3 and 12 months post-LTx. Samples were HLA typed (SSO, One Lambda Inc.) then screened for antibodies by single antigen beads for HLA, including C1q (One Lambda Inc.), HLA compatibility was assessed using HLAMatchmaker (version 2.1) and de novo donor specific antibodies (DSA) were determined using a MFI cut off >500. Results: HLA antibodies were detected pre-transplant in 21/49 patients (43%); 7 with Class I, 2 with Class II and 12 with both Class I&II, and four patients having pre-transplant DSA. 13/49 (27%) developed de novo HLA DSAs by 3 months post LTx; 1 with Class I, 8 with Class II, 4 with Class I&II. At 12 months post-transplant 5/49 patients had de novo class II DSA, with all having eplet scores greater than 40 for class II. When DSA development was correlated with eplet mismatch no significance was observed at Class I, however DRB1⁄ /DQA&B eplet mismatches correlated to HLA Class II DSA formation when using a cut-off of P40, at 3 months (p = 0.008) and at 12 months (p = 0.02). The C1q assay was positive for 5/12 de novo class II samples at 3 months post-transplant and 1/5 at 12 month all showing HLA-DQ specificities. There was no association with HLA antibody levels and the early measures of LTx outcomes, ICU and hospital days or acute rejection rates at 3 months post LTx. Conclusions: Having previously shown that high class II eplet mismatches is associated with RAS, we now show that the same factors are associated with de novo HLA class II DSA early post-Tx and that these levels are dynamic over time. We postulate that the RAS phenotype of CLAD may represent chronic AMR. G. Westall: 1. Grant/Research Support; Company/Organization; One Lambda.
P047
STABILITY OF ANTI-A2 BLOOD GROUP SUBTYPE TITERS AMONG BLOOD GROUP B CANDIDATES Harold C. Sullivan a, Christina L. Dean a, Scott M. Krummey a, Reuben P. Jacob a, Abigail L. Goodman a, Howard M. Gebel b, Robert A. Bray b. aEmory University, Atlanta, GA, United States; bEmory University Hospital, Atlanta, GA, United States. Aim: Kidney allocation based on blood type inadvertently disadvantages ABO B blood group candidates due to their disproportionate representation on the waitlist. To mitigate this situation, OPTN/UNOS modified the allocation system such that group B candidates could receive kidneys from group A2 or A2B donors if their anti-A titers are <1:8. Currently, anti-A titers must be monitored and recorded on UNetTM every 3 months. There is little evidence in the literature regarding measurement and stability of ABO titers and institutional practices remain variable. Our aim was to monitor the variability of anti-A titers of group B recipients over time and provide data to help guide practice in an evidence-based manner. Methods: Anti-A titer information and candidate demographics were reviewed from blood bank records. Patients included in the study were group B, renal allograft candidates who had P2 anti-A titers performed between January 2011 and December 2014. An anti-A titer of >1:8 excluded a group B candidate from receiving an out of group allograft. Variability in titers was assessed by delta dilution change between assays. Results: Anti-A titers were assessed on 193 group B, renal allograft candidates with P2 anti-A titers. Following the first titer, 50 patients (26%) were ineligible (i.e.,titer >1:8). Of the remaining 143 patients, 19 (13%) became ineligible following a second titer reaching >1:8. Forty patients (28%) had no delta dilution change between titers and 72 (50%) had a titer change that never reached >1:8. Only 12 patients (6% of total) experienced a titer change that affected eligibility after the second test. Conclusions: Although the majority of patients experience some variability in their anti-A titers over time, in most cases the variability does not affect their eligibility to receive an out of blood group renal allograft. Furthermore, the likelihood of a titer change affecting eligibility after two tests is limited to a small subset of patients. Our data suggest that testing of anti-A titers more than twice may not be necessary to effectively monitor recipient eligibility.
P046
Abstracts / Human Immunology 78 (2017) 51–254
HLA CLASS II EPLET MISMATCH PREDICTS DE NOVO DSA FORMATION AT 3 AND 12 MONTHS POST LUNG TRANSPLANT Duncan Walton a, Steven Hiho a, Linda Cantwell a, Joseph Ta a, Monika Loskot b, Tracy Phan b, Bronwyn Levvey b, Greg Snell b, Miranda Paraskeva b, Glen Westall b. aAustralian Red Cross Blood Service, West Melbourne, Australia; bThe Alfred Hospital, Melbourne, Australia. Aim: The aims of this prospective study were: 1) investigate a cohort of LTx recipients for the presence and clinical associations anti-HLA antibodies 2) Examine association between HLA eplet mismatch and HLA de novo antibody formation. Methods: From Jul 2014-Aug 2015, 49 patients were enrolled at time of listing for LTx, and blood samples obtained pre-transplant and at 3 and 12 months post-LTx. Samples were HLA typed (SSO, One Lambda Inc.) then screened for antibodies by single antigen beads for HLA, including C1q (One Lambda Inc.), HLA compatibility was assessed using HLAMatchmaker (version 2.1) and de novo donor specific antibodies (DSA) were determined using a MFI cut off >500. Results: HLA antibodies were detected pre-transplant in 21/49 patients (43%); 7 with Class I, 2 with Class II and 12 with both Class I&II, and four patients having pre-transplant DSA. 13/49 (27%) developed de novo HLA DSAs by 3 months post LTx; 1 with Class I, 8 with Class II, 4 with Class I&II. At 12 months post-transplant 5/49 patients had de novo class II DSA, with all having eplet scores greater than 40 for class II. When DSA development was correlated with eplet mismatch no significance was observed at Class I, however DRB1⁄ /DQA&B eplet mismatches correlated to HLA Class II DSA formation when using a cut-off of P40, at 3 months (p = 0.008) and at 12 months (p = 0.02). The C1q assay was positive for 5/12 de novo class II samples at 3 months post-transplant and 1/5 at 12 month all showing HLA-DQ specificities. There was no association with HLA antibody levels and the early measures of LTx outcomes, ICU and hospital days or acute rejection rates at 3 months post LTx. Conclusions: Having previously shown that high class II eplet mismatches is associated with RAS, we now show that the same factors are associated with de novo HLA class II DSA early post-Tx and that these levels are dynamic over time. We postulate that the RAS phenotype of CLAD may represent chronic AMR. G. Westall: 1. Grant/Research Support; Company/Organization; One Lambda.
P047
STABILITY OF ANTI-A2 BLOOD GROUP SUBTYPE TITERS AMONG BLOOD GROUP B CANDIDATES Harold C. Sullivan a, Christina L. Dean a, Scott M. Krummey a, Reuben P. Jacob a, Abigail L. Goodman a, Howard M. Gebel b, Robert A. Bray b. aEmory University, Atlanta, GA, United States; bEmory University Hospital, Atlanta, GA, United States. Aim: Kidney allocation based on blood type inadvertently disadvantages ABO B blood group candidates due to their disproportionate representation on the waitlist. To mitigate this situation, OPTN/UNOS modified the allocation system such that group B candidates could receive kidneys from group A2 or A2B donors if their anti-A titers are <1:8. Currently, anti-A titers must be monitored and recorded on UNetTM every 3 months. There is little evidence in the literature regarding measurement and stability of ABO titers and institutional practices remain variable. Our aim was to monitor the variability of anti-A titers of group B recipients over time and provide data to help guide practice in an evidence-based manner. Methods: Anti-A titer information and candidate demographics were reviewed from blood bank records. Patients included in the study were group B, renal allograft candidates who had P2 anti-A titers performed between January 2011 and December 2014. An anti-A titer of >1:8 excluded a group B candidate from receiving an out of group allograft. Variability in titers was assessed by delta dilution change between assays. Results: Anti-A titers were assessed on 193 group B, renal allograft candidates with P2 anti-A titers. Following the first titer, 50 patients (26%) were ineligible (i.e.,titer >1:8). Of the remaining 143 patients, 19 (13%) became ineligible following a second titer reaching >1:8. Forty patients (28%) had no delta dilution change between titers and 72 (50%) had a titer change that never reached >1:8. Only 12 patients (6% of total) experienced a titer change that affected eligibility after the second test. Conclusions: Although the majority of patients experience some variability in their anti-A titers over time, in most cases the variability does not affect their eligibility to receive an out of blood group renal allograft. Furthermore, the likelihood of a titer change affecting eligibility after two tests is limited to a small subset of patients. Our data suggest that testing of anti-A titers more than twice may not be necessary to effectively monitor recipient eligibility.