Aim: Autologous flow cytometric crossmatches (AutoXMs) are currently being used to interpret unexpected positive allogeneic flow cytometric crossmatches (AlloXMs) that may otherwise rule out transplantation between compatible donor-recipient pairs. At our institution, an AutoXM is routinely performed in tandem to an AlloXM. We aimed to 1) assess the benefit to routinely performing an AutoXM; 2) identify characteristics of patients more likely to experience false positive AlloXM and 3) evaluate outcomes of patients transplanted with a positive AutoXM.
Method: We retrospectively examined the demographics and native disease on 1,684 patients (4,143 AlloXMs) who were evaluated for a kidney, pancreas or combined (SPK) transplantation between April 2015 and May 2023
Results: Out of the 1,684 patients, 47 (2.8%) had positive AutoXMs for T, B or T&B cells. Among these 47 patients, 22 (47%) were exclusively B-cell positive and 13 (28%) were both T and B cell positive. Additionally, 34 (72%) of the 47 patients had intermittent positivity, 20 (43%) also had a positive AlloXM, 12 (26%) had a previous allograft, and 2 (4%) were HIV positive. Diabetes Mellitus, IgA nephropathy, and Glomerulonephritis were the native diseases that ranked highest among the positive AutoXMs, with 12, 6, and 6 patients, respectively. AutoXM positivity was not associated with cPRA. Of the 47 patients with a positive AutoXM, 44 were transplanted of which 43 (98%) have a functioning allograft . Post-transplant, 34 patients had no DSA at baseline and 7 (16%) developed de novo DSA.
Conclusion: Overall, our study examines an extensive number of AutoXMs to make inferences that will be helpful when interpreting unexpected positive AlloXMs.
