Comparison of symmetric dimethylarginine with creatinine, cystatin C and their eGFR equations as markers of kidney function

Abstract

Objectives Symmetric dimethylarginine (SDMA) is a catabolic product of arginine-methylated proteins and is an emerging biomarker for kidney function. A limited number of studies in selected populations have shown good correlation between SDMA and a few known markers of glomerular filtration rate (GFR). However, a comprehensive comparison of SDMA with all existing serum endogenous markers in a population with varied kidney function and against measured GFR is lacking. The objective of this study was to compare the correlations of SDMA, creatinine, cystatin C and their eGFR equations against GFR measured by iothalamate clearance in an adult population with varied kidney function. Design & methods Left-over serum and plasma specimens were collected from 40 adults with normal and reduced kidney function. GFR was measured using a radioactive iothalamate procedure. Creatinine and cystatin C were measured on Roche Cobas 8000. SDMA was measured by a published liquid chromatography-tandem mass spectrometry method. Results SDMA correlated highly with measured GFR (r = − 0.84), which was better than creatinine (r = − 0.70) but equivalent to cystatin C (r = − 0.86) and the eGFR equations [MDRD and CKD-EPI (separate and combined)]. Conclusions SDMA is a strong marker of kidney function and further studies are needed to establish an eGFR formula that includes it for widespread clinical use.