The GFR is used in clinical practice and research as the main tool for diagnosing, staging and managing CKD as well as for defining CKD-related prognosis and mortality risk. GFR is estimated using equations using the serum creatinine level. However accurate, GFR estimation may require confirmatory tests of which currently available include equations based on Cystatin C, urinary or plasma clearance of markers of exogenous filtration or urinary creatinine clearance. Here, CST3 is linked to chronic kidney disease.