[Subclinical acute rejections in protocol biopsies at 3 months after kidney transplantation]

The primary aim of the study was detection of subclinical acute rejection and borderline changes in protocol biopsies at 3 months after transplantation, and assessment of possible clinical and laboratory associations.

Biopsy was carried out in 194 patients with stabilized graft function. Patients were treated with immunosuppressive regimen based on cyclosporine A (n = 34), tacrolimus (n = 152), or sirolimus/everolimus (n = 10). Samples were processed by standard paraffine technique, and stained according to laboratory protocol. All samples were tested by immunofluorescence or immunohistochemical procedures for C4d presence as a sign of humoral rejection.

Of 192 representative samples, subclinical acute rejection and borderline changes were found in 24 samples (12.5%). In patients with this finding, the mean serum creatinine was significantly higher (185.2 +/- 2.2 micromol/L), than in patients with normal finding (128.2 +/- 28.3 micromol/L) p < 0.001. Using the ROC curve analysis of serum creatinine, the cut-off point 170 micromol/L was found to discriminate normal findings from subclinical rejection and borderline changes. A significant correlation between acute rejections before protocol biopsy and subclinical acute rejections together with borderline changes in protocol biopsy was found. C4d positivity was found in 6 samples. Immunosuppressive therapy (cyclosporine versus tacrolimus) did not have any impact on subclinical acute rejections and borderline changes prevalence.

The main conclusion of this study is a finding, that acute rejection early after renal transplantation and serum creatinine > or = 170 micromol/l at three months after transplantation are risks for development of subclinical acute rejection, even of humoral type, or borderline changes.