#48-OR
PRA OR TRANSPLANTABILITY INDEX - WHAT DO OUR CLINICAL COLLEAGUES NEED?
Gareth Page BSc MSc , Mieke van Dam MSc PhD , Alasdair Heads BSc and Robert Vaughan MSc PhD . London United Kingdom, Guy
s Hospital, SE1 9RT, Clinical Transplantation Laboratory .
Clinicians are familiar with the term Panel Reactive Antibody (PRA), but do they really understand what it means? PRA is used to indicate the transplantability of a patient, but the increasing range of anti-HLA screening and identification techniques has made complement dependent cytotoxicity PRA obsolete: Does the PRA include HLA class II antibodies or take antibody isotype into account? Is the panel static or random?
We would like to propose a novel way of assessing the transplantability of a patient.
Like many other laboratories, we use a simple flow cytometry based antibody screening technique as the first line in antibody detection. If antibody is present we employ a range of techniques (CDC, ELISA and Flow) to define the specificity. The key to transplantability is not only PRA, but a combination of recipient HLA type (compared to the donor population) and antibody specificity (directed at HLA in the donor population).
Using the UK guidelines for matching, the HLA antigen frequency (HLA A, B, DR) was calculated for local donors over a 3 year period. This was used to generate a phenotype score for patients on the transplant waiting list. Values ranged from 1 for HLA B70 (B71+72) to 50 for HLA A2. The computed score gives a matchability value for each patient.
A score for antibody specificity, based on adding the phenotype score of each individual specificity, is subtracted from the matchability value, giving a Transplantability Index (TI) for each patient.
The system applies to both national and local waiting lists. Antibody specificity must be determined, which reduces the number of unexpected positive crossmatches and reduces cold ischaemic time where kidneys are exported for sharing. Our TI gives clinicians precise information regarding the possibility of transplanting a particular patient.