Serum symmetric dimethylarginine in older dogs: Reference interval and comparison of a gold standard method with the ELISA

Abstract Background Serum symmetric dimethylarginine (SDMA) is used to screen for renal dysfunction in dogs. The gold standard technique for measuring SDMA, liquid chromatography‐tandem mass spectrometry (LC‐MS/MS) is not widely available. Age‐specific reference intervals for SDMA in older dogs are lacking. Objectives Prospective study in older dogs to validate a commercially available LC‐MS/MS method for SDMA, compare SDMA concentrations with concentrations measured using ELISA and obtain a reference interval (RI) for older dogs using both methods. Animals Client‐owned older dogs undergoing health screening. Methods The LC‐MS/MS method was analytically validated (limit of detection, precision, and linearity). Serum was sent cooled overnight for ELISA or was frozen at −80°C until batch analysis using LC‐MS/MS. Results of LC‐MS/MS and ELISA were compared and RIs for older dogs were calculated according to international guidelines. Results The LC‐MS/MS method showed good linearity (r2 = .99) and precision (coefficient of variation