DONOR-SPECIFIC ANTIBODIES AFTER TRANSPLANTATION BY FLOW-CYTOMETRY - RELATIVE CHANGE IN FLUORESCENCE RATIO MOST SENSITIVE RISK FACTOR FOR GRAFT-SURVIVAL

Background, There is no consensus on the role of donor-directed antibo dies after renal transplantation detected by complement-dependent cyto toxicity (CDC) or by flow cytometry (FC). Methods, Therefore, antibody formation was studied by FC and correlated with clinical course in a group of patients who received transplants between 1983 and 1993, All had a negative current CDC crossmatch and were treated with cyclospori ne. Current and posttransplant sera from 143 donor-recipient combinati ons were studied retrospectively. Antibodies were considered present i n FC if the fluorescence ratio between serum and negative control was >2.65, Results, Of 143 patients, 17 (11.9%) were found to be positive in the posttransplant FC crossmatch and 126 (88.1%) were negative, Of the positive patients, 3 were already positive in the current FC cross match, whereas 14 demonstrated a positive posttransplant FC crossmatch after a negative current FC crossmatch, It was noteworthy that, from 16 patients with a positive current FC crossmatch, 13 turned negative in the posttransplant crossmatch, In 113 recipients (79%), both pre- a nd posttransplant FC crossmatches were negative, The development of a positive FC crossmatch after transplantation was a significant risk. f actor for graft survival in Cox regression analysis (P=0.01), The resu lts were also studied as relative change in fluorescence ratio (RCFR), RCFR was determined by classifying the recipients in quartiles accord ing to their change in flow cytometric value from current to posttrans plant serum, Quartiles were defined as follows: quartile 1, decrease > 10%; quartile 2, decrease 0-10%; quartile 3, increase >0-30%; and quar tile 4, increase >30%, RCFR proved to be the only significant risk fac tor for graft survival (odds ratio for quartile 4 vs. quartile 1, 3.27 ; P<0.02), More rejections were shown for increasing quartile numbers (P<0.001), Conclusions, Classification of patients by RCFR detected mo re patients with unfavorable clinical outcome (25% vs. 11%) than by FC crossmatch.