CAN PROSPECTIVE CROSSMATCHES BE WAIVED?
HM Gebel and RA Bray, LSUMC, Shreveport, LA and Emory University Hospital, Atlanta, GA.
Following the landmark study of Patel and Terasaki (N Engl J Med 14:735, 1969), pre-transplant crossmatching became a 24/7 practice. Regulating organizations (ASHI;UNOS) mandate pre-transplant crossmatching for selected solid organs. Recently, this policy has been challenged. Specifically, two papers (Transplantation 66:1833; 1998 and Transplantation 66:1835; 1998) advocate that non-sensitized individuals be transplanted without a final crossmatch, a strategy designed to reduce ischemia time and decrease the risk of delayed graft function. The concept was predicated exclusively upon results generated with cytotoxicity based antibody screening techniques. As we and others have reported, flow cytometric based assays are more sensitive approaches to detect alloantibodies. More importantly, an increasing number of reports document that graft survival is improved among those patients transplanted when donor crossmatches were cytotoxicity negative/flow negative compared to patients transplanted when crossmatches were cytotoxicity negative/flow positive. Thus, some patients considered to be non-sensitized when analyzed by cytotoxicity may have alloantibodies when assessed by flow. In this study, panel reactive antibody (PRA) testing was performed on sera from 527 potential transplant recipients (303 renal; 224 cardiac). PRA evaluations were initially performed using an antiglobulin-enhanced cytotoxicity test (AHG-CDC); results were then compared to a flow based assay in which solublized HLA antigens were affixed to microparticles. By AHG-CDC, 302/527 (57%) patients exhibited 0% PRA. Among these patients, 76/302 (25%) were positive for class I or class II antibodies by flow cytometry. Retrospective flow cytometric crossmatches were positive in 11/30 patients, all of whom had been transplanted without prospective crossmatches based on having had 0% PRA by AHG-CDC. While the concept of transplanting non-sensitized patients without a prospective final crossmatch is appealing, our data demonstrate that how a patient is deemed to be non-sensitized is critical. We recommend that transplant centers hoping to waive prospective final crossmatches do so only when flow cytometric techniques have been applied to document that patients are non-sensitized.