Ladies and gentlemen,
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During May 14-18 the yearly EFI meeting was held in Florence, Italy. At the meeting, which attracted the highest number of participants ever, the role of non-HLA antibodies in transplantation was one of the favorite topics and was discussed both in oral presentations as well as a very well attended Teaching Class.
New techniques for detecting HLA and non-HLA ab
The Teaching Class was chaired by Professor Frans Claas, Leiden and Professor Rene Duquesnoy, Pittsburgh, and discussed the role of HLA and non-HLA antibodies in solid organ transplantation. During his presentation Frans Claas said that although the cytotoxic crossmatch is a contraindication to transplantation, the relevance of HLA antibodies detected by new techniques is not always clear and that they are a risk factor rather than a contraindication.
The results from new techniques should be carefully interpreted. There are conflicting data regarding the relevance of for example HLA antibodies detected in solid phase assays and there is currently no consensus around these assays. For example there is no standardization of definitions of a negative and a positive sample, the importance of complement or non-complement fixing antibodies etc. He also mentioned that for example bead based assays are difficult to standardize due to that the density of HLA molecules are different on the individual beads.
Rene Duquesnoy discussed match making in kidney transplantation, claiming that epitopes rather than HLA allele groups are important to match for in transplantation. For those further interested in structurally based HLA matching, more information and links to the HLA matchmaker program can be found at http://www.hlamatchmaker.net/.
As last speaker at the teaching class, Dr Anat Tambur of Northwestern University Hospital in Chicago, IL talked about the role of non-HLA ab in organ transplantation. Quite some time was spent on XM-ONE®, the only available CE marked and FDA registered crossmatch test for identification of donor specific endothelial cell antibodies. A more detailed presentation on XM-ONE® was presented by Dr Tambur at a subsequent AbSorber lunch seminar.
FCXM, an aid to successful transplantation
Separate from the Conference AbSorber hosted a lunch meeting focusing on Flow Cytometry based crossmatching in organ transplantation. Dr Andrea Harmer, Head of H&I, NHS Blood & Transplant, Sheffield, UK, explained that FCXM is a sensitive test which contributes to the risk assessment for organ transplantation. Dr Harmer said that FCXM is especially valuable in sensitized patients and doing a donor workup in these patients without FCXM would leave out essential data. Dr Harmer concluded FCXM is not a bar to transplantation; it is an aid to successful transplantation.
Establishing local cut-off values
Dr Anat Tambur presented the data from their ongoing study of XM-ONE® at Northwestern. A pilot study with 75 tests in 53 patients has been performed in patients on the waiting list. During the study, Northwestern have determined their own cut-off values for the assay, arriving in the channel shift of 64 channels as being positive for endothelial cell antibodies, both for IgG and IgM. In short, their current cut-off values have been statistically established by running twenty different HLA negative and MICA negative sera. With clinical data accumulating in the tested patients they will later correlate their XM-ONE ® results with clinical outcome to derive to more valuable clinical cut-off values. A comment from Dr Susan Fuggle, Nuffield Department of Surgery at the University of Oxford, UK said that when they had also established their local cut-off for XM-ONE® they had arrived at almost the same values.
Clinical cut-off values are of course the second step, evaluating a number of transplanted patients and correlate the XM-ONE® result with clinical outcome. This is an ongoing project at Northwestern and they are currently performing XM-ONE® in all their living donors and Dr Tambur said that they will be able to do so later during the year. At this point in time they only have one month data in 30 patients and any conclusions are too early to be made.
XM-ONE® proficiency testing
Reliable crossmatch results are essential in organ transplantation and access to a proficiency testing program where laboratories can benchmark their results serves an important function accomplishing this. AbSorber has, in close collaboration with the Eurotransplant Laboratory in Leiden, NL, performed a pilot study in order to develop proficiency testing for XM-ONE®. At the AbSorber lunch meeting, Professor Ilias Doxiadis from The Eurotransplant Reference Laboratory, Leiden, NL, presented data from the pilot study, including eight European Laboratories. Crossmatch results using XM-ONE® including CD3 and CD19 have been evaluated. In order to standardize the results between laboratories MESF beads has been included in the testing. The pilot has been successful in many ways and the laboratories has in general reached consensus. The inclusion of MESF in the PT seems to add a lot of value. The pilot will now be evaluated and refined and AbSorber is aiming to be able to offer this through Eurotransplant during the latter half of the year.
Frans Claas, who chaired the lunch meeting, concluded that XM-ONE® has evolved further during the last year and that it is now being used even more, also in a clinical setting. The planned proficiency testing is an important step towards a standardization of the assay.
For further details on the XM-ONE® proficiency testing, please contact us.
Scientific posters at the EFI meeting
Three different posters including XM-ONE® were presented at EFI. Mats Alheim and coworkers at Karolinska University Hospital, Stockholm, Sweden, had a poster on detection of complement factor deposition on lymphocytes and endothelial cells with XM-ONE®. From Centro Histocompatibilidade Norte, Porto, Portugal, Paula Xavier presented their work suggesting that the detection of AECA with XM-ONE® identifies a subgroup of HLA-ab negative patients undergoing acute rejection. Maria Kafetzi , General Hospital, Athens, Greece presented their work with XM-ONE® in AB0 incompatible kidney transplant comparing AB0 incompatible patients with compatibles. All these posters will be available on AbSorber webpage shortly.
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