Kidney function estimating equations in patients with chronic kidney disease.

The current guidelines emphasise the need to assess kidney function using predictive equations rather than just serum creatinine. The present study compares serum cystatin C-based equations and serum creatinine-based equations in patients with chronic kidney disease (CKD). Seven hundred and sixty-four adult patients with CKD were enrolled. In each patient serum creatinine and serum cystatin C were determined. Their glomerular filtration rate (GFR) was estimated using three serum creatinine-based equations [Cockcroft-Gault (C&G), modification of diet in renal disease (MDRD) and the Chronic Kidney Disease Epidemiology Collaboration equation (CKD-EPI)] and two serum cystatin C-based equations [our own cystatin C formula (GFR=90.63 × cystatin C(-1.192) ) and simple cystatin C formula (GFR=100/cystatin C)]. The GFR was measured using (51) CrEDTA clearance. Statistically significant correlation between (51) CrEDTA clearance with serum creatinine, serum cystatin C and all observed formulas was found. The receiver operating characteristic curve analysis (cut-off for GFR 60 ml/min/1.73m(2)) showed that serum cystatin C and both cystatin C formulas had a higher diagnostic accuracy than C&G formula. Bland and Altman analysis for the same cut-off value showed that all formulas except simple cystatin C formula underestimated measured GFR. The accuracy within 30% of estimated (51) CrEDTA clearance values differs according to stages of CKD. Analysis of ability to correctly predict patient's GFR below or above 60 ml/min/1.73m(2) showed statistically significant higher ability for both cystatin C formulas compared to MDRD formula. Our results indicate that serum cystatin C-based equations are reliable markers of GFR comparable with creatinine-based formulas.

Hojs R ，Bevc S ，Ekart R ，Gorenjak M ，Puklavec L ... -  《-》

Simple cystatin C formula compared to sophisticated CKD-EPI formulas for estimation of glomerular filtration rate in the elderly.

Despite the fact that the serum creatinine level is notoriously unreliable for the estimation of glomerular filtration rate (GFR) in the elderly, the serum creatinine concentration and serum creatinine-based formulas, such as the Modification of Diet in Renal Disease study equation (MDRD) are the most commonly used markers to estimate GFR. Recently, serum cystatin C-based formulas, the newer creatinine formula (the Chronic Kidney Disease Epidemiology Collaboration formula (CKD-EPI creatinine formula), and an equation that uses both serum creatinine and cystatin C (CKD-EPI creatinine and cystatin formula) were proposed as new GFR markers. The aim of our study was to compare the MDRD formula, CKD-EPI creatinine formula, CKD-EPI creatinine and cystatin formula, and simple cystatin C formula (100/serum cystatin C) against (51) Cr-EDTA clearance in the elderly. A total of 317 adult Caucasian patients aged >65 years were enrolled. In each patient, (51) Cr-EDTA clearance, serum creatinine, and serum cystatin C were determined, and the GFR was calculated using the MDRD formula, CKD-EPI formulas, and simple cystatin C formula. Statistically significant correlations between (51) Cr-EDTA clearance and all formulas were found. In the receiver operating characteristic (ROC) curve analysis with a cut-off of GFR 45 mL/min/1.73 m(2), a higher diagnostic accuracy was achieved with the equation that uses both serum creatinine and cystatin C (CKD-EPI creatinine and cystatin formula) than the MDRD formula (P < 0.013) or CKD-EPI creatinine formula (P < 0.01), but it was not higher than that achieved for the simple cystatin C formula (P = 0.335). Bland and Altman analysis for the same cut-off value showed that the creatinine formulas underestimated and the simple cystatin C formula overestimated measured GFR. All equations lacked precision. The accuracy within 30% of estimated (51) Cr-EDTA clearance values differ according to the stage of CKD. Analysis of the ability to correctly predict GFR below and above 45 mL/min/1.73 m(2) showed a high prediction for all formulas. Our results indicate that the simple cystatin C formula, which requires just one variable (serum cystatin C concentration), is a reliable marker of GFR in the elderly and comparable to the creatinine formulas, including the CKD-EPI formulas.

Bevc S ，Hojs R ，Ekart R ，Gorenjak M ，Puklavec L ... -  《-》

Simple cystatin C formula compared to serum creatinine-based formulas for estimation of glomerular filtration rate in patients with mildly to moderately impaired kidney function.

Serum cystatin C (SCC)-based formulas and the newer creatinine formula (the Chronic Kidney Disease Epidemiology Collaboration formula (CKD-EPI)) were proposed as improved glomerular filtration rate (GFR) markers. The aim of our study was to compare serum creatinine (SCr)-based and SCC-based equations against (51)Cr-EDTA clearance in patients with mildly to moderately impaired kidney function. 255 adult Caucasian patients with chronic kidney disease (GFR 89-30 ml/min/1.73 m(2)) were enrolled. In each patient, (51)Cr-EDTA clearance, SCr and SCC were determined. GFR was calculated using the Cockcroft-Gault (C&G), Modification of Diet in Renal Disease (MDRD), CKD-EPI formulas and simple cystatin C formula (SCCF) (100/SCC). The receiver-operating characteristic curve analysis (cut-off for GFR 60 ml/min/1.73 m(2)) showed that the SCCF had a higher diagnostic accuracy than C&G but not than MDRD or CKD-EPI formulas. The Bland-Altman analysis for the same cut-off value showed that creatinine formulas underestimated and SCCF overestimated the measured GFR. Analysis of ability to correctly predict a patient's GFR <60 or >60 ml/min/1.73 m(2) showed the higher ability for the SCCF compared to all creatinine-based formulas. Our results indicate that the SCCF is a reliable marker of GFR and comparable to creatinine formulas including the CKD-EPI formula.

Bevc S ，Hojs R ，Ekart R ，Gorenjak M ，Puklavec L ... -  《-》

Serum cystatin C as an endogenous marker of renal function in patients with mild to moderate impairment of kidney function.

Hojs R ，Bevc S ，Ekart R ，Gorenjak M ，Puklavec L ... -  《NEPHROLOGY DIALYSIS TRANSPLANTATION》

Diagnostic accuracy of various glomerular filtration rates estimating equations in patients with chronic kidney disease and diabetes.

Li HX ，Xu GB ，Wang XJ ，Zhang XC ，Yang JM ... -  《-》