Background: Human leukocyte antigen (HLA) donor-specific antibodies (DSA) play a crucial role in the risk assessment of antibody-mediated rejection and graft survival in kidney transplantation. However, the significance of HLA non-donor specific antibodies (non-DSA) detected by the Single Antigen Bead (SAB) method in predicting transplant outcomes remains undetermined This single-center study aimed to evaluate the impact of both DSA and non-DSA identified using the SAB method on the outcome of living related renal allograft recipients.
Methods: A retrospective analysis of prospectively collected data was conducted on a cohort of living related renal allograft recipients(LRRAR) transplanted between May 2017 and December 2021 at SGPGI Lucknow. Recipients of ABO incompatible allograft and those who did not complete one year follow-up were excluded. The institute follows a cost-effective pre-transplant immunological evaluation as in (figure 1a). The presence of DSA and non-DSA was determined based on the SAB results. Desensitisation protocols, Induction regimen were based on institute protocols (figure 1b). The primary endpoint was incidence of BPAR in patients with non-DSAs in comparison to those with DSA, and secondary outcomes included the incidence of graft and patient survival, Infection related hospitalisations, outcomes in comparison with non-sensitised patients. 
Results: Among the 413 LRRAR in the study period ,85(20.6%) ABO incompatible allografts were excluded. Among the ABO compatible, 4.8% tested positive for HLA DSA ( either alone or along with other non-DSAs) by SAB while 11.1% had HLA non-DSAs and the rest(63.4%) were non-sensitised. In our cohort the mean(SD) age was 45.2 (7.1) years, spousal donors contributed to 38% of the donor pool, the median dialysis vintage was 24 (0 – 80) months, 4.8% second transplant recipients, 78% received >2 blood transfusions and 8.5% multiparous women. Among those with DSAs , 16 (80%) required plasma exchange and rituximab desensitisation while none with non DSA underwent desensitisation. ATG induction was used in 37% ( 34.8 Vs 40, p 0.5). The median duration of follow-up was 37 (2-37) months. Early BPAR(<1 month) was noted in 31.8% (non-DSA 28.3% Vs DSA 40%, p <0.001), BPAR (1-12 months) seen in 25% (30.4 Vs 15%, p <0.001) and BPAR beyond 1st year in 12.2% (13% Vs 10%, p0.2). The death censored graft survival at last follow-up was (8.7% Vs 10%, p 0.74) and mortality rate at end of follow-up was 8.5%(6.5% Vs 10%,p 0.86). The kaplan meier graft and patient survival curves are depicted for those with DSA, non-DSA and unsensitised patients. (figure 2).
Conclusion: We found that there is a high incidence of biopsy proven acute rejection in those who had non-DSA HLA antibodies and possible reasons for this could be due to Cross reactive antibodies.  We suggest that complete immunological work-up including Single antigen bead testing when done as part of a cost-effective protocol like ours may provide valuable actionable information for better graft outcomes. Such cost-effective protocols should also enable wide-scale application of testing for CREGs and eplet matching “ Being fore-warned is fore-armed”