[Noninvasive diagnostic and predictive value in renal transplant recipients with acute rejection by measurement of urine Fractalkine].

Objective: To investigate the relationship between early-stage renal acute rejection(AR) and the level of Fractalkine in urine, explore the diagnostic and noninvasive monitoring value in early stage after transplantation by measurement of urine Fractalkine. Methods: Urine samples were examined from renal transplant patients between January 2006 and October 2009. A total of 155 patients were enrolled, including 49 with biopsy-proved AR, 58 patients with stable renal function and no abnormal histological findings, 10 patients with subclinical rejection in protocol biopsy, 9 patients with biopsy-proven acute tubular necrosis and 29 patients with biopsy-proven chronic allograft nephropathy. Additionally, urine samples were also collected from 40 healthy controls. Fractalkine was measured in urine samples using a commercial human Fractalkine enzyme-linked immunosorbent assay (ELISA) kit. Immunohistochemistry for Fractalkine expression was performed on biopsies from renal transplant patients with AR and non-AR. Results: Forty-nine patients with AR excreted urinary Fractalkine at a significantly higher level than levels in patients with stable renal function and healthy controls[(429.1±56.1)vs (94.6±8.4), (84.5±8.9)ng/mmol creatine, both P <0.001]. Patients with AR excreted urinary Fractalkine at a significantly higher level than levels in patients with acute tubular necrosis and chronic allograft nephropathy[(429.1±56.1)vs(133.0±9.8), (183.0±18.9)ng/mmol creatine, both P <0.001]. Receiver operating characteristic(ROC)curve was constructed to determine the discriminatory power of Fractalkine levels for diagnosis of AR. The area under ROC curve was 0.920(95% CI : 0.875-0.969, P <0.001), which showed that Fractalkine was a suitable marker for the diagnosis of AR. At a cut-off point of 157.5 ng/mmol creatinine, the sensitivity was 83.7% and the specificity was 84.5% ( P <0.001). The dynamic level of urinary Fractalkine in AR patients within 3 weeks after transplantation fluctuated above 300 ng/mmol creatine, which is remarkably higher than patients with stable renal function (below 200 ng/mmol creatinine). Conclusions: As a noninvasive monitoring method, Fractalkine in urine may be a new approach for detection of AR as well as useful to predict response to antirejection therapy. It has good sensitivity and specificity. Besides, measurement of Fractalkine in urine is a simple, inexpensive method for the routine clinical monitoring after kidney transplantation.