Analysis of fine-needle aspiration biopsies by flow cytometry in kidney transplant patients.

Background: Peripheral blood lymphocyte (PBL) analysis by flow cytometry has been inconsistently reported as an adjunctive method for diagnosing acute kidney transplant rejection. However, there is good evidence that lymphocytes infiltrating renal grafts differ from those found at the peripheral level. We hypothesized that the study of aspiration biopsy samples in conjunction with PBL by flow cytometry would enable us to diagnose acute rejection crisis reliably.

Methods: Lymphocytes from PBL and aspiration biopsies of kidney transplant patients were analyzed. Fifty-one stable patients, rejection-free for the first 6 months, were studied on day 7 and day 30 after transplantation and were compared with 32 patients with 40 acute rejection episodes.

Results: Significant 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 differentiating the two groups of patients. By combining the expression of several activation markers inside the graft with CD3DR and CD3CD25 aspiration biopsy to peripheral blood ratios, we obtained very good values for sensitivity and specificity-83.9% and 90.5%, respectively. The positive predictive value for rejection among dysfunctional grafts reached 85.8%.

Conclusions: Flow cytometry study of aspiration biopsy samples of kidney transplant patients is a reliable and powerful method to diagnose acute rejection episodes, although it is needed to consider several lymphocyte phenotypes; cytofluorometric analysis of PBL is important because it provides graft-infiltrating cell to peripheral blood lymphocyte ratios. This safe and rapid test may significantly improve the management of kidney transplant patients.