334 Virtual crossmatching for pancreas transplantation is immunologically safe and reduces organ ischaemic time.
Monday November 16, 2015 from 15:30 to 17:00
Room 110

Petros Yiannoullou, United Kingdom

Transplant Surgical Trainee

Department of Transplantation

Manchester Royal Infirmary


Virtual crossmatching for pancreas transplantation is immunologically safe and reduces organ ischaemic time.

Petros Yiannoullou1, Zia Moinuddin1, Hussein Khambalia1, Giuseppe Giuffrida1, Angela Summers1, Tunde Campbell1, Ravi Pararajasingam1, Bence Forgacs1, Afshin Tavakoli1, David van Dellen1, Titus Augustine1, Stephen Sheldon1, Judith Worthington1, Raman Dhanda1, Kay Poulton1.

1Department of Transplantation, Central Manchester Foundation Trust, Manchester, United Kingdom

Background: Hyperacute rejection results from pre-formed donor-directed antibodies to Human Leukocyte Antigens (HLA), and is avoided by performing a pre-transplant crossmatch. This involves the incubation of donor lymphocytes with recipient sera, detecting any donor-directed reactivity due to the presence of HLA antibodies in the recipient. Crossmatching is performed either by complement dependent cytotoxicity (CDC) or Flow Cytometry.

Luminex assays use synthetic microspheres coated with HLA antigens to capture antibodies present in a serum sample, offering enhanced specificity and sensitivity to traditional methods. Therefore, HLA specificities that would be unacceptable can be avoided. Using Luminex-based antibody screening, it is acceptable to predict that a patient who has no HLA specific antibodies would be crossmatch negative, and could safely be transplanted without the need for a laboratory crossmatch, providing that the recipient has not experienced any potential sensitising events since their last serum sample. This is the basis of the Virtual Crossmatch (VXM).

VXM can be extended to include patients with clearly defined HLA antibody profiles. Using the Single Antigen Bead test, a complete antibody profile can be clearly recorded and regularly updated for each patient. When a donor offer is received, the donor HLA type can be compared with the HLA antibody profile of the patient. This carries much greater immunological risk, relying upon precise HLA typing of the donor. If a patient is transplanted on the basis of a VXM, the laboratory crossmatches are performed as soon as possible after receipt of crossmatch material. VXM allows the patient to be taken to theatre as soon as the organs arrive, eliminating the 4-6 hour delay caused by a pre-transplant crossmatch and reducing total ischaemic time (TIT).

Methods: A retrospective analysis of all solid-organ pancreas transplants performed between 1st January 2009 and 31st December 2014 was undertaken.  Data on crossmatch type, TIT and donor hospital distance were collated and analysed. For patients who had a VXM, retrospective CDC crossmatches were performed on all patients, and Flow Cytometry crossmatches were also performed on sensitised patients with a reaction frequency of >50%.

Results: 159 pancreas transplants were performed in the specified time period.  97 (61%) patients were transplanted on the sole basis of a negative VXM result.  A pre-transplant wet crossmatch (CDC/Flow) was performed in the remaining 62 (39%) cases.  Median TIT in the VXM group was 620.5minutes versus 888 minutes in the wet crossmatch group (p<0.0001). There was no significant difference in donor hospital distance.  100% of the VXM group had subsequent negative retrospective CDC/Flow crossmatch results.  There was a significant increase in the use of VXM for pancreas transplant during the study period (p<0.0001).

Year VXM CDC/Flow Total
2009             9 (50%)        9 (50%)           18
2010             12 (60%)        8 (40%)           20
2011             12 (40%)       18 (60%)           30
2012             10 (36%)       18 (64%)           28
2013             27 (77%)        8 (23%)           35
2014             27 (96%)        1 (4%)           28
Total             97 (61%)        62 (39%)           159

Conclusions: The increased use of VXM at our centre has been immunologically safe and significantly reduced TIT resulting in improved outcomes following pancreas transplantation. In our experience, the increased risk of performing a VXM in a sensitised patient is far outweighed by the benefit of reducing the TIT.

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