Plasma total C-terminal agrin fragment (tCAF) as a marker for kidney function in patients with chronic kidney disease

Background: Total C-terminal agrin fragment (tCAF) is a new biomarker that was previously correlated with kidney function. This article studies the validity of tCAF as a biomarker for kidney function in chronic kidney disease (CKD). Methods: Plasma tCAF, serum creatinine (Cr), cystatin C (CyC), blood urea-nitrogen (BUN) concentrations and estimated glomerular filtration rate (eGFR CKD-EPI_{crea-cystatin}) were assessed in 426 individuals [71 without CKD (CKD 0°) and 355 CKD patients]. In addition to descriptive statistics, univariate correlation between tCAF and biomarkers/eGFR was calculated; multiple linear regression modeling was applied between logarithmic (log) tCAF and log eGFR and adjusted for demographic data. The same methods were used to analyze the association of demographic factors and the different biomarkers adjusted for eGFR. Results: Mean tCAF levels were 1012.2±789.9 pM. tCAF correlated with all biomarkers/eGFR in univariate analysis (eGFR: r = -0.77, Cr: r = 0.74, BUN: r = 0.66, CyC: r = 0.75). Linear regression modeling revealed an excellent coefficient estimate between log tCAF and log eGFR (CKDEPI_{crea-cystatin}) (-0.91, p < 0.001). tCAF was the parameter least associated with demographic parameters in both univariate and multivariate regression modeling (only with age, coefficient estimate r = -0.159, p = 0.001 in multivariate regression). Conclusions: In conclusion, tCAF is a promising biomarker for the assessment of kidney function in CKD patients showing an excellent correlation with eGFR and being less influenced by demographic parameters compared to conventional biomarkers. These preliminary results encourage further evaluation of tCAF in larger CKD cohorts and other clinical settings such as acute renal failure.