Simultaneous Quantification of Serum Symmetric Dimethylarginine, Asymmetric Dimethylarginine and Creatinine for Use in a Routine Clinical Laboratory.

Abstract

Background Symmetric dimethylarginine (SDMA) and asymmetric dimethylarginine (ADMA) are naturally occurring amino acids classed as uremic toxins by the EUTOX working group. SDMA is principally excreted through the kidneys and is a well-known renal function marker, ADMA is a potent inhibitor of nitric oxide production. Here, we describe the development of a rapid and sensitive liquid chromatography tandem mass spectrometry method for simultaneous measurement of SDMA, ADMA and creatinine. Method Serum samples were prepared by protein precipitation and dilution with acetonitrile prior to injection onto a Waters TQS-Micro. Multiple reaction monitoring was used to detect SDMA, ADMA, creatinine, and their corresponding internal standard transitions after separation with a HILIC analytical column. Sample stability and intra-individual variation studies were also assessed following ethical approval. Results The retention time for creatinine was 0.43, SDMA 1.10 and ADMA 1.14 minutes. Mean recovery for creatinine was 103%, SDMA was 100% and ADMA was 103%, matrix effects were minimal (<6%). Lower limit of quantitation for creatinine and SDMA/ADMA was 17.5 µmol/L and 0.1 µmol/L respectively. Analytical imprecision showed a coefficient of variation <10% for all analytes across the working range of the assays. Intra-individual variation for creatinine was 4.7%, SDMA 7.5% and ADMA 7.6%. Discussion We have developed a rapid assay for LC-MS/MS measurement of SDMA, ADMA and creatinine in a routine clinical laboratory. It is simple, reproducible, and easy to perform. The stability of SDMA and ADMA pre- and post-centrifugation allows for their routine use without any special sample handling requirements.