Creatinine production rate (CPR) and glomerular filtration rate (GFR) estimates from serum cystatin C and creatinine in the groups of controls (C), patients with renal failure (RF), renal transplant (RTx), heart failure (HF), biliary obstruction (BO), liver transplant (LTx), and critical illness (CI). Here, CST3 is linked to hydrops fetalis.