P126 Comparison study of CDC and flow crossmatch vs. donor specific antibodies in transplantation

Abstract

Aim Our approach to transplant highly sensitized patients has been to perform CDC crossmatch (XM) when the results of flow xm are above 200 mean channel shifts (MCS) with donor specific antibodies (DSA). The aim of our study was to determine if the flow crossmatch and solid phase antibody testing can be used as the only measures for decisions to transplant. Methods Results of flow xm, CDC xm and solid phase DSA testing were analyzed for 44 donor and recipient pairs. In all cases, the flow xm were positive with greater than 200 MCS values. Undiluted patient sera were tested by Luminex single antigen (LSA) test for HLA antibodies (ABS). The ABS detected by this method were grouped into weak (MFI 2500–5000) moderate (MFI 5000–7500), and strong (MFI 7500-greater than 17000). The CDC xm was performed with and without DTT treatment using the same sera for flow xm. Results In 70% of this group with positive T and/or B CDC xm at least one DSA detected was in the strong binding range above 17,000 MFI. In 30% of cases multiple DSA detected in weak to moderate range below 7500 MFI values. In 50% of neg T cell and 96% of neg B cell CDC crossmatches, the MFI of DSA detected was in moderate to strong range. In 90% of negative CDC xms the MCS values for flow T was below 300 and flow B below 400 MCS. The range of flow MFI values for positive CDC B cells xm was 156–596 and 238–671 for T cells. Conclusions While the CDC xm test is the classical standard to exclude transplant, it is not always a reliable test. This assay is quite subjective and dependent on quality and strength of complement, technical skills of the laboratory technician and donor cell viability. This assay is also not reliable when patient is under desensitization therapy. There is a need to develop this assay using flow cytometer platform. Use of solid phase testing methods and determination of standards for decision to transplant based on number, type and strength of antibodies can be a better method