ANALYSIS OF FINE-NEEDLE ASPIRATION BIOPSIES BY FLOW-CYTOMETRY IN KIDNEY-TRANSPLANT PATIENTS

Background. Peripheral blood lymphocyte (PBL) analysis by flow cytomet ry has been inconsistently reported as an adjunctive method for diagno sing acute kidney transplant rejection. However, there is good evidenc e that lymphocytes infiltrating renal grafts differ from those found a t the peripheral level. We hypothesized that the study of aspiration b iopsy samples in conjunction with PBL by flow cytometry would enable u s to diagnose acute rejection crisis reliably. Methods. Lymphocytes fr om PBL and aspiration biopsies of kidney transplant patients were anal yzed. Fifty-one stable patients, rejection-free for the first 6 months , were studied on day 7 and day 30 after transplantation and were comp ared with 32 patients with 40 acute rejection episodes. Results. Signi ficant differences were observed for several lymphocyte subpopulations on aspiration biopsy samples comparing stable patients with rejection patients, In contrast, PBL analysis was not helpful in differentiatin g the two groups of patients. By combining the expression of several a ctivation markers inside the graft with CD3DR and CD3CD25 aspiration b iopsy to peripheral blood ratios, we obtained very good values for sen sitivity and specificity-83.9% and 90.5%, respectively. The positive p redictive value for rejection among dysfunctional grafts reached 85.8% . Conclusions. Flow cytometry study of aspiration biopsy samples of ki dney transplant patients is a reliable and powerful method to diagnose acute rejection episodes, although it is needed to consider several l ymphocyte phenotypes; cytofluorometric analysis of PBL is important be cause it provides graft-infiltrating cell to peripheral blood lymphocy te ratios. This safe and rapid test may significantly improve the mana gement of kidney transplant patients.