Predicting residual kidney function in hemodialysis patients using serum β-trace protein and β2-microglobulin

Abstract

Residual kidney function (RKF) contributes significant solute clearance in hemodialysis patients. Kidney Diseases Outcomes Quality Initiative (KDOQI) guidelines suggest that hemodialysis dose can be safely reduced in those with residual urea clearance (KRU) of 2 ml/min/1.73 m(2) or more. However, serial measurement of RKF is cumbersome and requires regular interdialytic urine collections. Simpler methods for assessing RKF are needed. β-trace protein (βTP) and β2-microglobulin (β2M) have been proposed as alternative markers of RKF. We derived predictive equations to estimate glomerular filtration rate (GFR) and KRU based on serum βTP and β2M from 191 hemodialysis patients based on standard measurements of KRU and GFR (mean of urea and creatinine clearances) using interdialytic urine collections. These modeled equations were tested in a separate validation cohort of 40 patients. A prediction equation for GFR that includes both βTP and β2M provided a better estimate than either alone and contained the terms 1/βTP, 1/β2M, 1/serum creatinine, and a factor for gender. The equation for KRU contained the terms 1/βTP, 1/β2M, and a factor for ethnicity. Mean bias between predicted and measured GFR was 0.63 ml/min and 0.50 ml/min for KRU. There was substantial agreement between predicted and measured KRU at a cut-off level of 2 ml/min/1.73 m(2). Thus, equations involving βTP and β2M provide reasonable estimates of RKF and could potentially be used to identify those with KRU of 2 ml/min/1.73 m(2) or more to follow the KDOQI incremental hemodialysis algorithm.

Estimating of Residual Kidney Function by Multi-Frequency Bioelectrical Impedance Analysis in Hemodialysis Patients Without Urine Collection

“…To the best of our knowledge our study is the first to use BIA measurements to predict RKF in MHD patients. Our new equation showed improvements in bias compared to those of Hoek et al [10], Vilar et al [11] and Wong et al [12] equations in their sample. The best constructed regression equation using BIA measurements before and after hemodislysis session could explain 75% of mGFR variance.…”

“…Overall, our equation showed the good performance in estimating mGFR in the study population– i.e., the low median bias, the high precision, the moderate accuracy and the high CCC. However, limits of agreement are still wide as in middle molecular weight biomarkers based equations for RKF estimation [10-12]. This suggests that our equation may not be accurate enough to estimate RKF.…”

“…Since gold-standard measures of kidney function such as inulin clearance or radioisotope clearance techniques are technically difficult and impractical for routine clinical use, alternative methods to estimate residual GFR were developed [6, 10-12]. The European Best Practice Guidelines (EBPG) recommends calculating residual GFR as the mean of creatinine and urea clearance based on interdialytic urine collection, and corrected for body surface area [6].…”

“…Recently, poorly dialyzable middle molecules based methods to assess RKF without reliance on urine collections were proposed [10-13]. Equations for calculating residual GFR using Cystatin C [10], β2-microglobulin [11-12] and b-trace protein [12] serum concentrations have been developed. However, the use of these biomarkers to date is not common, expensive and may be time consuming.…”

Increasing Haemodialytic Clearances as Residual Renal Function Declines: An Incremental Approach

“…Thus, there has been renewed interest in trying to develop serum-based RRF assessments. Two equations have been recently proposed, using serum biomarkers including β2M, β-trace protein and cystatin C [42,43] and have been validated as a pragmatic technique for estimating RRF, and developing this approach will allow more dialysis centres offer an incremental dialysis approach.…”