Correlation of Beta Trace Protein Levels with Serum Creatinine-Based Estimated Glomerular Filtration Rate Equations in Chronic Kidney Disease


Background. Estimated GFR (eGFR) is calculated using serum creatinine (SCr) based equations which have their own limitations. Novel biomarkers like beta trace protein (BTP) are studied for eGFR estimation. The aim of this study is to determine the serum levels of BTP in healthy controls and chronic kidney disease (CKD) cases and to find out the correlation of BTP levels with that of SCr and SCr-based eGFR formulas.
Methods. The control group comprised of 20 healthy adults. The cases comprised of 20 patients each in CKD stages 3, 4, and 5, categorized based on eGFR calculated using MDRD formula. Baseline characteristics of the study population were recorded. BTP was measured by ELISA (Enzyme Linked Immunosorbent Assay) method and SCr by modified Jaffe’s method. The statistical analyses were performed with the SPSS for Windows, version 16.0.
Results. The median value of blood urea nitrogen (BUN) in the cases was 26.50 mg/dL (IQR 19.25-37) and for control it was 9.5 mg/dL (IQR 8-12). The median value of SCr in the cases was 2.75 mg/dL (IQR 1.725-4.45) and in the controls, it was 0.7mg/dL (IQR 0.6 -0.8). The median value of BTP in cases was 6389.25 ng/ml (IQR 5610.875-10713.75) and in controls, it was 1089.5 ng/ml (IQR 900.5-1309.75).
Conclusion. Serum BTP levels correlated with SCr levels and renal function. We could establish the relationship between the two biomarkers, SCr and BTP, and derive a regression equation.

Keywords: Beta trace protein, estimated GFR, CKD, correlation


Any structural or functional abnormalities of the kidneys that persist beyond 3 months irrespective of the etiology is defined as chronic kidney disease (CKD) [1]. In clinical practice, renal function is assessed indirectly using serum creatinine (SCr) values and SCr-based glomerular filtration rate (GFR) equations. The ‘gold standard’ for GFR estimation, the inulin clearance cannot be used routinely, because of the difficult and cumbersome nature of the procedure. Serum cystatin C based equations have also been recently developed [2, 3]. Notable equations are Cockroft-Gault formula, Chronic Kidney Disease Epidemiology (CKD-EPI) equation and Modification of Diet in Renal Disease Study (MDRD) equation [46]. However, each equation has its own inherent limitations such as a lack of accuracy, precision, and variations with ethnicity [78].

Factors such as protein intake and muscle mass determine SCr levels. Due to lower muscle mass, SCr levels are lower in women and in older individuals. SCr level has a curvilinear relationship with GFR because of its tubular secretion in mild-to-moderate degrees of renal failure. A SCr value of 1.5 mg/dl could represent a GFR of anywhere between 30-90 ml/min. Such wide range of eGFR is not acceptable and hence, SCr-based assays are not considered ideal. The need for better biomarkers need not be overemphasized. 

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