CST3 and chronic kidney disease: Many studies have described and compared the diagnostic performance of BTP with the traditional markers of CKD [13,14,15], reporting that increased urinary and systemic BTP concentrations were highly correlated with creatinine and cystatin C concentrations [16,17]; moreover, the urinary concentration of BTP progressively increased, along with GFR reduction, and with a rise in its serum concentration [16].