Relationship between Serum Symmetric Dimethylarginine Concentration and Glomerular Filtration Rate in Cats

BackgroundDirect measurement of glomerular filtration rate (GFR) is the preferred method to assess renal function in cats, but it is not widely used in the diagnosis of chronic kidney disease (CKD). In cats with CKD, symmetric dimethylarginine (SDMA) has been shown to increase and to correlate with plasma creatinine concentrations. HypothesisIn cats, reduced GFR corresponds with increased serum SDMA concentration. AnimalsThe study group consisted of ten client-owned cats whose GFR had been measured previously. Cats ranged in age from 11.1 to 16.9years; both azotemic and nonazotemic animals were included. MethodsGlomerular filtration rate was determined for each cat by plasma iohexol clearance using the three sample slope-intercept method, and serum SDMA concentration was measured by liquid chromatography-mass spectrometry. ResultsA linear relationship was observed between GFR and the reciprocal of serum SDMA concentration (R-2=0.82, P<.001). A similar relationship was found between GFR and the reciprocal of plasma creatinine concentration (R-2=0.81, P<.001). Conclusions and Clinical ImportanceIncreased serum SDMA concentrations were observed in cats with reduced renal function as determined by direct measurement of GFR. This finding indicates that SDMA could have clinical applications in the diagnosis of CKD in cats.