6.6
TITLE: PANEL–REACTIVE ANTIBODY AND RENAL TRANSPLANT BIOPSY RESULTS

H. J. Noreen,¹ M. Krefting,¹ A. J. Matas,² M. Segall.<sup>3

1</sup>Immunology Laboratory, Fairview–University of Minnesota Medical Center, Minneapolis, MN; ²Surgery, University of Minnesota, Minneapolis, MN; ³Laboratory Medicine/Pathology, University of Minnesota, Minneapolis, MN

The development of anti–HLA antibodies post–renal transplantation (Tx) has been suggested to indicate poor Tx outcome. We tested for panel–reactive antibodies (PRA) at time of renal biopsy (Bx) for elevated creatinine, to determine whether PRA results would be helpful in determining the nature and/or predicting the outcome of the presumed rejection episode. Between 8/1997 and 10/1998, blood samples were obtained from 98 recipients scheduled for Bx. Six patients were excluded from analysis. Included were 21 patients with no pathologic diagnosis (NPD); 27 with acute rejection treated with Solu–Medrol and/or prednisone; 4 with steroid–resistant acute rejection; 8 with acute rejection initially treated with antibody; 15 with chronic rejection; and 16 with “non–immunologic” diagnoses. Forty–five percent of the patients had received a Tx from a living donor. PRA results using an antiglobulin–augmented (AHG) cytotoxicity method were available on both Tx and Bx specimens for 91 of the 92 included patients. All recipients had a negative AHG crossmatch at Tx. There were few changes in PRA status between Tx and Bx (median interval, 7 months; range, 2 wk to 18.5 yr). Of the 91 analyzable recipients, 69% were PRA(–) at both Tx and Bx (PRA(–/–); 24% were PRA(+/+); 4% were PRA (+/–); and 2% were PRA(–/+). Of recipients with NPD, 14% were PRA(+) at Tx and 9% were PRA(+) at Bx, compared to 37% and 30% respectively for those with any type of rejection, and 33% and 26% for those with acute rejection. The odds ratio for any Bx result other than NPD was 3.06 for recipients PRA(+) at Tx and 3.99 for recipients PRA(+) at Bx. The odds ratios for any diagnosis of rejection were 2.03 and 1.86, respectively. None of these were statistically significant. Similar results were obtained with a subset of 71 patients for whom ELISA–based PRA results were available. Our data indicate that a positive PRA at either Tx or Bx is not significantly associated with Bx results, although it may further increase the clinician’s index of suspicion in the event of a post–Tx rise in creatinine. For this latter purpose, the PRA result at transplant seems sufficient. There were few changes in PRA status, and antibody continued to be present, in some cases after many years of immunosuppression.