Validity of Estimated Glomerular Filtration Rates for Assessment of Baseline and Serial Renal Function in Patients With Atherosclerotic Renal Artery Stenosis

Abstract

Background-Despite routine use of estimated glomerular filtration rates (GFRs) as major renal end points in clinical trials of renal revascularization, serial GFR estimates have never been validated in patients with renal artery stenosis (RAS). The purpose of this study was to evaluate the validity of GFR estimates in patients with atherosclerotic RAS. Methods and Results-Serum creatinine (SCr) and 125 I-iothalamate GFR (I-GFR) were measured in patients with RAS. GFR estimates were calculated from Modification of Diet in Renal Disease (MDRD), Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI), and Cockroft-Gault (CG) formulas. Using I-GFR as the reference standard, the sensitivity, specificity, and receiver operating characteristic area under the curve (AUC) were determined for MDRD, CKD-EPI, CG, and reciprocal SCr for identifying I-GFR Ͻ60 mL/min per 1.73 m 2 and a 20% change in I-GFR over time. Between 1998 and 2007, 541 I-GFR measurements were performed in 254 consecutive patients with RAS. MDRD, CKD-EPI, and CG GFR estimates demonstrated good sensitivity (86% to 95%), modest specificity (67% to 71%), and good reliability (AUC, 0.86 to 0.94) for identifying I-GFR Ͻ60 mL/min per 1.73 m 2 . GFR estimates had good specificity (87% to 95%), poor sensitivity (0% to 45%), and poor reliability (AUC, 0.61 to 0.65) for detecting 20% changes in I-GFR over follow-up. Conclusions-In patients with RAS, GFR estimates demonstrate good sensitivity and modest specificity for identifying I-GFR Ͻ60 mL/min per 1.73 m 2 but poor sensitivity and reliability for detecting 20% changes in I-GFR. GFR estimates should not be used in clinical trials as major end points to assess serial GFR after renal revascularization. (Circ Cardiovasc Interv. 2011;4:219-225.)

Effects of Stenting for Atherosclerotic Renal Artery Stenosis on eGFR and Predictors of Clinical Events in the CORAL Trial

“…Thus, the risk-benefit tradeoff of stenting among patients with high-risk ARAS is uncertain. Questions about reproducibility and accuracy of GFR estimated from measures of serum creatinine and the validity of a 20% decline in eGFR as an end point for studies in ARAS have been raised (33). A recent report of using both serum cystatin C and serum creatinine found substantially improved accuracy and precision for eGFR calculated by the CKD-EPI equation across a wide range of eGFR levels (15).…”

The Management of Renal Artery Stenosis: An Alternative Interpretation of ASTRAL and CORAL

“…In the presence of unilateral RA disease the contralateral kidney is capable of compensatory change, and contralateral renal hypertrophy may obscure change in the functional result of both kidneys and may cancel out changes induced by the stenotic kidney. 11 RA disease is linked to the increasing systemic atherosclerosis in the ageing population. 12,13 Increased prevalence of ostial lesions is associated with aortic atherosclerotic disease and thrombus formation that may have already injured end-organs from progressive atheroembolization.…”

Attending Rounds

“…Let me emphasize that creatinine changes related to even moderate volume shifts, diuretic use, and/or RAAS blockade are magnified in the presence of renovascular disease. These changes likely reflect the kidney functioning near the limits of autoregulation of both blood flow and GFR beyond critical stenosis (23).…”