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ABOUT-K STUDY – A PROSPECTIVE STUDY OF ABO INCOMPATIBLE KIDNEY
TRANSPLANTS. DOES TITRE ASSAY VARIABILITY AFFECT CLINICAL
OUTCOMES BETWEEN DIFFERENT UK TRANSPLANT CENTRES?
Bentall, A¹, Barnett, N², Braitch, M¹, Briggs, D³, Mamode, N², Ball, S¹
¹Queen Elizabeth Hospital, Birmingham, ²Guys and St Thomas Hospital, London,
³NHSBT, Birmingham
INTRODUCTION: UK antibody incompatible registry data suggests poorer outcomes in
ABOi recipients reported internationally data. Nevertheless this remains a potentially
important treatment strategy particularly for blood group O recipients who inevitably
accumulate in a paired exchange scheme. We propose that comparison of antibody levels
between centres might indicate different levels of risk for patients.
METHOD: The ABOUT-K multicentre observational study of ABOi transplantation
includes patients recruited from 10 centres in the UK. Local ABO titres against donor were
measured, and a parallel sample sent to a central laboratory at timepoints including: preinduction, pre-extracorporeal antibody removal therapy (EART) and pre-transplant. Patients
were treated according to local protocols. 100 patients recruited received an ABOi kidney
transplant. For central ABO quantification a standardised, NHSBT approved Gel card method
(Diamed) was used by a single operator.
RESULTS: The mean age of recipients was 48.1± 13.6years, 41% were female, 68% were
blood group O with 59% A1 donors. 1 year follow-up time has been reached in 80% patients.
The median local titre against donor at baseline was 32 (range 0-512) and at transplantation
was 4 (0-64). 58% of patients received IA vs 28% PEx (either PEx or DFFP). The mean titre
dilution per EART was 1.4±1.2 (IA) and 1.8±1.5(PEx). 1 year patient survival is 98.9% and 1
year DCGS is 95.5%. Graft loss was higher in patients with titres >1:64 dilution at baseline,
but this did not reach significance. Despite local titre reproducibility (graph 1) and wide range
of local to central titre variability(graph 2), neither the local nor the central ABO titre
predicted rejection at time of transplant. Acute rejection occurred in 25.5% of recipients of
which 22.9% this was reported as being antibody mediated. 1 year creatinine in patients
reaching following up is 132.7 ± 46.2 micromol/L.
Graph 1
Graph 2
CONCLUSION: Despite poor national data, in this study, 1 year patient and graft survival
were comparable to live donor outcomes. There was no significant difference between local
and central titres at each time point, with a wide range of titres treated. There was no
significant difference in patient or allograft outcomes in patients with higher titres. The
outcome of this study would suggest that there is an association of graft loss with higher
titres, although this study did not have enough endpoints to confirm this.