CST3 and chronic kidney disease: Kidney Disease: Improving Global Outcomes (KDIGO) has recommended the use of the 2012 Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine-cystatin C equation to estimate GFR when we have to know more accurate GFR such as confirming a diagnosis of chronic kidney disease (CKD) for the first time and adjusting dosage of possibly toxic drugs that are mainly excreted by kidney [16,17].