Different impact of pretransplant anti-HLA antibodies detected by Luminex in highly sensitized renal transplanted patients

Stability of Anti-HLA Sensitization Profiles in Highly Sensitized Kidney Transplantation Candidates: Toward a Rational Serological Testing Strategy

BACKGROUND

Highly sensitized (HS) anti-HLA patients awaiting kidney transplantation benefit from specific allocation programs. Serological monitoring at 3-mo intervals is recommended to prevent unexpected positive crossmatch (XM), but this strategy is not evidence-based. Therefore, we assessed its relevance when using single-antigen flow bead (SAFB) and screening flow bead (SFB) assays.

METHODS

We included 166 HS patients awaiting a transplant and assessed their SAFB profile during the year preceding their inclusion. Anti-HLA antibodies were evaluated by SAFB assay and compared within patients as serum pairs at 3, 6, and 9 mo. We assessed the performance of SFB for detecting changes in SAFB profiles with 35 serum pairs.

RESULTS

On comparing 354, 218, and 107 serum pairs at 3, 6, and 9 mo, respectively, only 0.6%, 0.7%, and 1% of all antigens tested exceeded for the first time the unacceptable antigen threshold (mean fluorescence intensity ≥2000) in the most recent sample. Irrespective of the follow-up period, the calculated panel-reactive antibodies increased by a mean of 1%, and there was no significant increase in the proportion of donors at risk for positivity of flow- or complement-dependent cytotoxicity XM. The SFB did not accurately detect the variations of SAFB profiles.

CONCLUSIONS

Changes in HS patient profiles are anecdotal and show little association with transplant access or risk for positive XM. Less-frequent monitoring in HS patients should be considered to improve cost-effectiveness without affecting transplant safety.

Disparity in the access to kidney transplantation for sensitized patients in the state of Sao Paulo-Brazil

Highly sensitized (HS) patients accumulate on deceased donor kidney transplantation (DDKT) waitlists worldwide due to matching difficulty and inequity of allocation policies. Current situation of HS patients on KT waitlist in Brazil has not been published. All patients enrolled on the KT waitlist of the State of São Paulo from 2002 to 2017 were retrospectively assessed. Patients were divided into eight groups according to their degree of sensitization, PRA of 0%, >0-40%, >40-80%, >80-85%, >85-90%, >90-95%, >95-98% and > 98%. Cumulative incidence curves for transplantation or mortality/removal from waitlist were estimated by competing risk. Among 50,249 waitlisted candidates, 1247 prioritized, 2467 with age < 18 or > 75 years and 4152 submitted to living-donor KT were excluded from the analysis, remaining 42,383 patients. There were 29,664(70%) PRA 0%, 5611(13.2%) PRA > 0-40%, 3442(8.2%) PRA > 40-80%, 507(1.2%) PRA > 80-85%, 564(1.3%) PRA > 85-90%, 825(1.9%) PRA >90-95%, 859(2%) PRA > 95-98% and 911(2.2%) PRA > 98%. There was a progressive increase in the need of prioritization, waiting time for KT or on waitlist and time on dialysis as PRA increased (p < 0.001). Probability of DDKT clearly increased as PRA decreased so that PRA 0% candidates were much more likely to be transplanted compared to PRA > 98% patients(HR:13.02, p < 0.001). Waiting list mortality/removal was higher among PRA > 0-40%(HR1.05,p = 0.03), PRA > 90-95%(HR:1.10,p = 0.05), PRA > 95-98%(HR:1.26,p < 0.001) and PRA > 98%(HR:1.09,p = 0.05) patients compared to PRA zero candidates. HS patients in Sao Paulo-Brazil required greater prioritization due to lack of venous access, longer dialysis and waitlist times, lower probability of DDKT and higher rates of waitlist mortality/removal. We confirmed the disparity of access to KT among HS patients in Sao Paulo-Brazil, indicating the need of new strategies that optimize transplantation for this subcategory of patients.

How to improve the survival of the kidney transplant - is it only the pharmaceutical management?

Kidney transplantation is the best treatment option in chronic kidney disease patients. Despite the new potent immunosuppressants, the long-term graft survival has not significantly improved. This is a rather complex issue with interrelationship between pretransplant donor-recipient variables, recipient post-transplant perioperative non/immunological factors, the combination/dose of maintenance immunosuppression and the general noncompliance of the patient. The recipients with an increased immunological risk should be maintained on triple therapy with steroids, preferably tacrolimus (Tac) or cyclosporine (CsA) plus mycophenolate mofetil (MMF). Eventual calcineurin inhibitor (CNI) minimization should be coupled with either protocol biopsies or frequent biochemistry monitoring including periodical assessment of anti-human leukocyte antigen and donor-specific antibodies. Recipients with standard immunological risks may be considered for as low as possible triple immunosuppression (steroids, Tac/CsA, MMF) after a period of 6 - 12 months. In cases of CNI minimization, a modification with a higher dose of the other two drugs in the triple therapy combination might be considered. The nonadherence to the prescribed maintenance therapy should be regularly checked-up. In conclusion, antibody induction, MMF, steroids and low-dose Tac/CsA should be the mainstream therapy in majority of patients. The short- and mid-term encouraging results for CNI minimization/withdrawal seem to correspond to recent findings of chronic antibody-mediated rejection, and long-term results need further evaluation.