5-OR

Abstract

Aim Determinations of donor specific antibodies (DSA) from anti-HLA class-1 single antigen bead (SAB) assays are highly predictive of cross match (XM) outcomes. While negative screening bead assays routinely predict negative XMs and highly reactive DS SAB tests usually predict positive XMs, the laboratory, is however, faced with some cases where SAB assays do not reliably predict XM results. In one type of situation, a relatively high level of DSA is detected but the XM is un explicably negative. We hypothesized that this type of outcome could be due to a DSA that did not fix complement in the CDCXM. C1q assays were performed to investigate this issue. Methods XMs (n = 379) were routinely performed by CDC Amos one wash and on selected patients by flow cytometry for deceased donor kidney transplantation. Anti - HLA antibody detection and quantitation are performed with screening and SABs, respectively (Gen-Probe, CT). DSA calculations are performed by addition of the net MFI of all positive beads, net MFI reactivity score (NMRS). SAB assays for DSA that detects C1q reactive classes of IgG and the standard assay (One Lambda, CA) were performed on selected patients. Results Five XMs on 4 patients waiting for a deceased donor kidney with relatively high levels of DSA were evaluated by CDC Amos one wash. All five XMs were however negative. The calculated DSA (NMRS) was, in the standard SAB assay, respectively, for each donor: 18,259, 30,146, 18,806, 19,044 and 51,976. The C1q assays for all of these sera were negative whereas control sera tested at the same time were highly reactive. These potential recipients were transplanted as it is the general policy at our center not to transplant sensitized patients with DSA that would result in positive flow cytometry XMs. Conclusions Though the above situations occur in less than 2% of the XMs they involve considerably more laboratory time and effort. C1q tests should reduce the effort and uncertainty of correlating solid state antibody tests with XM outcome. Norin: Gen-Probe: Speakers Bureau.