Positive Luminex and negative flow cytometry in kidney transplantation: a systematic review and meta-analysis.

The presence of pre-formed donor-specific antibodies (DSAs) in kidney transplantation is associated with worse overall outcomes compared with DSA-negative transplantation. A positive complement-dependant cytotoxic crossmatch presents a high immunological risk, while a negative flow cytometry crossmatch is at the lower end of the risk spectrum. Yet, the presence of low-level DSA detected by Luminex alone, that is, positive Luminex and negative flow (PLNF) cytometry crossmatch lacks robust scientific exploration. In this systematic review and pooled analysis, we investigate the glomerular filtration rate, acute rejection (AR), graft survival and patient survival of PLNF transplants compared with DSA-negative transplants. Our analysis identified seven retrospective studies consisting of 429 PLNF transplants and 10 677 DSA-negative transplants. Pooled analysis identified no significant difference in the incidence of AR at 1 year [relative risk (RR) = 1.35, 95% confidence interval (CI) 0.90-2.02, Z = 1.46, P = 0.14, I2 = 0%], graft failure at 1 year (RR = 1.66, 95% CI 0.94-2.94, Z = 1.75, P = 0.08, I2 = 23%), graft failure at 5 years (RR = 1.29, 95% CI 0.90-1.87, Z = 1.38, P = 0.17, I2 = 0%), patient mortality at 1 year (RR = 0.89, 95% CI 0.31-2.56, Z = 0.22, P = 0.82, I2 = 0%) and patient mortality at 5 years (RR = 1.76, 95% CI 0.48-6.48, Z = 0.85, P = 0.39, I2 = 61%). Pooled analysis of graft function was not possible due to insufficient data. Current evidence suggests that low-level DSA detected by Luminex alone does not pose significant risk at least in the short-medium term. Considering the shortage of kidney transplants and the ever-increasing waiting time, the avoidance of PLNF transplants may be unwarranted especially in patients who have been enlisted for a long time.