MP308USING ESTIMATED GFR TO DIAGNOSE CKD STAGES: FLICKING THE COIN

Abstract

INTRODUCTION AND AIMS: The classification of Chronic Kidney Disease (CKD) categorizes chronic renal disease into five stages on the basis of estimated GFR (eGFR). CKD classification was intended to define the severity and extension of the disease, risk for progression, and to guide treatments of renal diseases. However, concerns have been expressed about the reliability of this classification. A major limitation is that it is based on eGFR, which has a low accuracy and precision to reflect real GFR. This may lead to errors in the classification of the stages of CKD. The aim of this study was to analyze the impact of the error eGFR in the classification of CKD. METHODS: We analyzed 514 patients with renal disease of diverse causes: type 2 diabetes, chronic glomeurlonephritis, nephroangioesclerosis, interstitial nephritis, renal transplantation, liver transplantation, and living kidney donors, among others. GFR was measured with the plasma clearance of iohexol and patients were classified in CKD stages based on measured GFR. Also, eGFR was calculated with 53 formulas based on creatinine and or cystatin-c and CKD stages were also defined based on eGFR. The error in the classification of CKD using eGFR by formulas was evaluated. RESULTS: Based on mGFR, 71 (14%) patients were in CKD-1; 159 (31%) in CKD-2; 182 (35%) in CKD-3; 87 (17%) in CKD-4 and 15 (3%) in CKD-5. In general, considering all formulas, only 40 to 70% of the patients were correctly classified in CKD stages. Thus, 30 to 60% of the cases were incorrectly classified into a consecutive lower or a higher stage of CKD. The misclassification into a non-consecutive stage was observed in 3-5% of the cases. The results of a subgroup of equations are shown in Table 1. Similar results were observed for the remaining equations (data snot shown). No major differences were observed with the use of more recent cystatin-c-based formulas. CONCLUSIONS: 1 or 2 patients out of 3 are incorrectly classified in the CKD stages by any formula. This makes the classification unreliable in clinical practice and research. Caution is needed with the use of the CKD classification based on eGFR. (Table Presented).