Symmetrical dimethylarginine is a more sensitive biomarker of renal dysfunction than creatinine

Current definitions of acute kidney injury (AKI) are based upon changes in serum creatinine (SCr) concentration and urine output: both have limitations in patients with AKI. Diagnosis may be delayed if using these criteria alone. We have previously validated a method of measuring the glomerular filtration rate (GFR) intended for use in patients with AKI (a continuous infusion of very low dose iohexol; CIVLDI). In this study we compare the performance of symmetrical dimethylarginine (SDMA) against SCr and CIVILDI. SDMA is the structural isomer of the endogenous nitric oxide inhibitor asymmetrical dimethylarginine. SDMA increases in parallel with SCr. Despite this, no formula exists to estimate GFR from SDMA concentration. Tubular secretion of SCr may be as high as 40%. SDMA may be a more sensitive biomarker of renal dysfunction than SCr; however, the tubular reabsorption of SDMA is unknown. The aims were to compare the performance of SDMA against SCr and accurately measured GFR, and to derive a formula to estimate GFR from SDMA concentration.