Serum symmetric dimethylarginine concentration in healthy neonatal Thoroughbred foals

Background Symmetric dimethylarginine (SDMA) is widely used in other species as a marker of renal dysfunction and is considered a more sensitive indicator of glomerular filtration rate than creatinine. Reference ranges are established in healthy adult horses (<= 14 mu g/dL) and concentrations are increased in horses with acute kidney injury (median 32 mu g/dL; range 15-92). Objectives To establish the normal range of SDMA concentrations in neonatal Thoroughbreds. Study design Cross-sectional. Methods Blood samples were collected from Thoroughbred foals Subjects included 120 foals. Median age was 13.5 h (range 1.0-34.0). Median and 95% confidence interval for SDMA concentration was 69.0 mu g/dL (63.0, 75.0; range 35.0-376.0). A cut-off value of 168 mu g/dL would include 95% of individuals and is therefore suggested. Serum SDMA concentration was correlated with age (R = -.3, P = .003), creatinine concentration (R = .6, P <= .001) and urea concentration (R = .3, P = .002). Main limitations Limitations include a small sample size, no consideration of subclinical disease and a short follow-up period. Conclusions In equine neonates, SDMA concentration is higher than in adult horses, older foals and adults with acute kidney injury. Therefore, currently SDMA cannot be used as a marker of renal dysfunction in this age group. Further work is required to assess whether SDMA concentration is increased in neonates with renal disease and, if so, what cut-off should be used.