P033 Cryopreserved donor cell crossmatches: Can we believe the results?

Abstract

Aim In order to facilitate rapid turnaround, exchange programs such as the NKR require preliminary flow cytometric crossmatching (FCXM) using frozen cells. However, we’ve found that questionable FCXM results occur more often with frozen cells compared to results obtained with fresh donor lymphocytes. In this study, we investigated the frequency of such discrepant results. We compared 17 donor/recipient pairs who were crossmatched using both frozen and fresh donor cells. Methods Fresh lymphocytes were isolated using EasySep™ (StemCell Technologies). Frozen cells were thawed following a validated protocol (ASHI Laboratory Manual). All cells were treated with pronase. FCXM were performed using a rapid protocol (Liwski, et al., H.I. 72, 2011). In all cases, a screening FCXM was performed with frozen cells and a final FCXM was performed with fresh donor cells. For final FCXM, one specimen tested in the initial screening FCXM was included. Donor specific antibodies (DSA) were analyzed using multiple solid phase platforms. Results Six out of the 17 FCXM comparisons were discrepant. Among the discrepant FCXM, 4/6 were T & B cell positive using frozen cells and negative using fresh cells; 1/6 had elevated, but within negative range, MCS using frozen cells and clearly negative MCS ( Conclusions The problem with unreliable frozen cell crossmatches is that false positive results can lead to unnecessary donor denial and false negative results can bring about last minute exchange failure. When a recipient clearly has no DSA, a positive FCXM using frozen cells is not typically problematic and most often a repeat FCXM using fresh cells is negative. On the other hand, for patients with DSA, the intent of an exploratory FCXM with frozen cells is to rapidly evaluate whether or not DSA strength is at an acceptable level. However, in order to be clinically informative, it is important that FCXM results using frozen cells correlate with fresh cells. Download : Download high-res image (279KB) Download : Download full-size image