The effect of low titers of donor-specific antibodies (DSAs) detected only by sensitive solid-phase assays (SPAs) on renal transplant outcomes is unclear. We report the results of a systematic review and metaanalysis of rejection rates and graft outcomes for renal transplant recipients with such preformed DSAs, defined by positive results on SPA but negative complement-dependent cytotoxicity and flow cytometry crossmatch results. Our search identified seven retrospective cohort studies comprising a total of 1119 patients, including 145 with isolated DSA-SPA. Together, these studies suggest that the presence of DSA-SPA, despite a negative flow cytometry crossmatch result, nearly doubles the risk for antibody-mediated rejection (relative risk [RR], 1.98; 95% confidence interval [CI], 1.36-2.89; P,0.001) and increases the risk for graft failure by 76% (RR, 1.76; 95% CI, 1.13-2.74; P=0.01). These results suggest that donor selection should consider the presence of antibodies in the recipient, identified by the SPA, even in the presence of a negative flow cytometry crossmatch result. In 1969, Patel and Terasaki published their landmark study that definitively established the detrimental effect of preformed donor-specific antibodies (DSAs) detected by complement-dependent cytotoxicity (CDC) crossmatch on short-term allograft survival, but they noted the limited sensitivity of the technique in the detection of preformed DSAs. 1 Since that time, technological advances have led to increasingly more sensitive tests for the detection of anti-HLA DSAs, including flow cytometry crossmatch and the more recent solid-phase assays (SPAs), such as Luminex. 2,3 The clinical significance of DSAs detected by sensitive SPA remains unclear, with disparate findings being reported in the literature. 4 Further, the clinical utility of these tests, particularly for prognostication or modifying immunosuppressive therapy, when used individually or in some sequential manner remains unclear. Our aim was to perform a systematic review and meta-analysis of published reports of rejection rates and graft outcomes among renal transplant recipients with preformed DSA at levels detectable only by SPA but not by CDC or flow crossmatch.
RESULTSWe ultimately identified seven studies that met our inclusion criteria for the primary quantitative analysis (group 1). [5][6][7][8][9][10][11] All seven studies were retrospective cohort studies; three were from the United States and four from Europe. Our ability to compare