Symmetric dimethylarginine (SDMA) is a stronger predictor of mortality risk than asymmetric dimethylarginine (ADMA) amongst older people with kidney disease

Background Circulating asymmetric (ADMA) and symmetric dimethylarginine (SDMA) are increased in patients with kidney disease. SDMA is considered a good marker of glomerular filtration rate (GFR) whilst ADMA is a marker of cardiovascular risk. However, a link between SDMA and all-cause mortality has been reported. In the present study we evaluated both dimethylarginines as risk and GFR markers in a cohort of elderly white individuals, both with and without CKD.

Methods GFR was measured in 394 individuals aged >74 years using an iohexol clearance method. Plasma ADMA, SDMA and iohexol were measured simultaneously using isotope dilution tandem mass spectrometry.

Results Plasma ADMA concentrations were increased (P<0.01) in people with GFR <60 mL/min/1.73 m² compared to those with GFR >60 mL/min/1.73 m², but did not differ (P>0.05) between those with GFR 30-59 mL/min/1.73 m² and <30 mL/min/1.73 m². Plasma SDMA increased consistently across declining GFR categories (P<0.0001). GFR had an independent effect on plasma ADMA concentration whilst GFR, gender, body mass index and haemoglobin had independent effects on plasma SDMA concentration. Participants were followed for a median of 33 months. There were 65 deaths. High plasma ADMA (P=0.0412) and SDMA (P<0.0001) concentrations were independently associated with reduced survival.

Conclusions Amongst elderly white individuals with a range of kidney function, SDMA was a better marker of GFR and a stronger predictor of outcome than ADMA. Future studies should further evaluate the role of SDMA as a marker of outcome and assess its potential value as a marker of GFR.