Our services for heart and/or lung transplantation
- HLA antibody profiles prior to the patient being accepted onto the transplant waiting list and regular antibody screening whilst on the waiting list.
- HLA -A, -B, -DR typing of patients accepted onto the waiting list.
- Prospective or virtual crossmatching with potential donors for patients with detectable HLA antibodies.
- Retrospective HLA-A, -B, -C, -DR, -DQ typing of donors and HLA-C, -DQ typing of recipients.
- Retrospective crossmatching for all patients with their donors.
- Post-transplant anti-HLA antibody profiles.
Techniques
HLA typing
We carry out DNA-based typing of HLA class I (A, B and C) and HLA class II (DRB and DQB) specificities using reverse sequence-specific oligonucleotide probes (SSO). HLA typing determines the HLA-A, -B, -C, -DR and -DQ types of recipients and donors for thoracic organ transplantation.
We have validated the molecular techniques we use as part of our participation in national quality assurance schemes.
Screening for HLA class I and class II antibodies
HLA antibody screening determines the level of sensitisation and specificity of class I and class II reactive antibodies present in a patient’s circulation. This provides a guide to the probability of a recipient being sensitised to potential donor HLA antigens in the UK donor population. It is a requirement before transplantation.
The presence of HLA antibodies with a clearly defined specificity, or combination of specificities, in the sera will exclude patients from receiving a donor expressing the HLA specificities with which the antibodies are reactive. We determine this by performing a virtual crossmatch prior to the transplant. Patients with antibodies which are poorly defined will require a prospective or virtual crossmatch before transplantation.
The presence of antibodies reactive with HLA class I (A, B and C) and class II (DR and DQ) antigens is primarily determined using a Luminex based system for IgG antibodies. If the screening is positive, we carry out further tests to identify the specificity and/or Ig class of the antibodies.
Donor crossmatching
The lymphocytotoxic crossmatch is a complement-dependent cytotoxicity assay that detects complement-fixing antibodies reactive with donor lymphocytes in the patient’s sera. A positive crossmatch indicates that the patient has preformed cytotoxic HLA antibodies directed against the donor HLA antigens. These are known to be associated with poor graft outcome in thoracic organ transplantation. A negative crossmatch indicates that there are no such antibodies present.
Prior to transplantation, when preformed HLA antibodies have a clearly defined specificity, the on-call tissue typist will determine if a donor is suitable by liaising with Organ Donation and Transplantation (ODT). We will carry out a virtual or prospective donor crossmatch as necessary. If antibody screening results are not in the patient notes or on the electronic patient record before transplant, these are available from the on-call tissue typist.
It is our policy to always perform a retrospective crossmatch with recipient sera against donor and autologous T, B and mixed lymphocytes. We perform crossmatching on the next working-day post-transplantation. On a case-by-case basis an urgent retrospective crossmatch and/or Luminex HLA antibody test should be considered (tested within 24 to 36 hours) where the results may be relevant to clinical decision making or patient management. Historical sera, including a sample taken within the 24 hours prior to transplant, are used in the procedure. In addition, for previously sensitised recipients, we perform a flow cytometric crossmatch on the next working-day post-transplantation. The flow crossmatch is a more sensitive test than the lymphocytotoxic crossmatch, detecting antibodies binding to donor T and B cells.
Target turnaround times
- HLA antibody screening – 90% of reports to be sent out within 14 days of sample receipt.
- Donor crossmatch – 90% of reports to be sent out within five days of transplant. A verbal result will be available within 48 hours of transplant.
- Donor HLA typing report – 90% of reports to be sent out within 21 days of transplant.
We audit these targets on a monthly basis and review them annually. We make every effort to provide accurate and informative results as quickly as possible.
View the Tissue Typing user guide (PDF, 454KB).