MO955: Serum Cystatin C in Renal Transplantation: Beyond GFR Estimation, A Prognosis Marker?

Abstract

Abstract BACKGROUND AND AIMS In renal transplantation, death with a functioning graft remains one of the main causes of graft loss. In the general population, renal function impairment is strongly associated with cardiovascular and all-cause mortality. Whether this association holds true for kidney transplant recipients (KTR) is unclear. This uncertainty is likely to be due, in part, to the fact that glomerular filtration rate (GFR) estimation based on serum creatinine (SCr) does not always provide an accurate evaluation of the graft function in KTR. As compared to SCr, we have previously shown in a large cohort of KTR that serum cystatin C (SCysC) is a much better marker of GFR. Herein, we sought to study the ability of the 1-year-post-transplant renal function to predict all-cause mortality according to the methods used to assess GFR. METHOD Four hundred and ten consecutive KTR for whom a measurement of GFR by inulin clearance was available at 1 year post-transplant were included. SCr and ScysC were measured with standardized methods. The association of the 1-year inulin clearance value the 1-year MDRD Study equation value and the 1-year CKD-EPI ScysC equation value with all-cause mortality was studied by ROC analysis and Cox model. RESULTS During a median follow-up of 17 years, 131 KTR died. Mean (±SD) inulin clearance at 1-year-post-transplant was 47 (±13) mL/min/1.73 m2. Areas under the ROC curves were similar for inulin and CKD-EPI ScysC equation values (0.62 for both), and were both significantly superior to that of the MDRD equation (0.54, P < 0.01). In Cox analysis, while all types of GFR evaluations were significantly associated to graft loss, only an inulin and a CKD-EPI ScysC equation values below 45 mL/min/1.73 m2 were associated with an excess risk of mortality (HR of 1.55, 1.45 and 1.01 for inulin, CKD-EPI ScysC and MDRD, respectively). CONCLUSION We conclude that ScysC-based GFR estimation might better predict KTR outcome as compared with a traditional SCr-based estimation. The one year-post transplant GFR value given by the CKD-EPI ScysC equation should be further evaluated as a potential surrogate marker for both graft and patient survival.