Symmetric dimethylarginine and creatinine concentrations in serum of healthy draft horses.
Authors: Schott Harold C, Gallant Lisanne R, Coyne Michael, Murphy Rachel, Cross Julie, Strong-Townsend Marilyn, Szlosek Donald, Yerramilli Maha, Li Jun
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary: SDMA as a renal marker in draft horses Symmetric dimethylarginine (SDMA) shows promise as an alternative to creatinine for assessing glomerular filtration rate in horses, though breed-specific variations warrant consideration when interpreting results. Researchers validated a commercial SDMA immunoassay against liquid chromatography-mass spectrometry in 165 healthy draft horses (Percherons, Clydesdales, and Belgians aged 0.5–16 years), demonstrating strong correlation between the two methods (R = 0.74). Whilst SDMA concentrations did differ significantly between breeds—Clydesdales showed higher values (median 10.2 µg/dL) compared to Percherons and Belgians (both 9.8 µg/dL)—these differences were clinically modest, and all medians remained well below the 14 µg/dL threshold used to indicate renal dysfunction in small animals. Neither sex nor age influenced SDMA or creatinine concentrations, suggesting that SDMA may offer a more stable renal marker than creatinine across diverse draft horse populations. For practitioners, these findings support SDMA as a complementary diagnostic tool in cases where subtle changes in renal function need detection; however, breed-specific reference ranges should be established before clinical application, and the applicability to non-draft horses requires further validation.
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Practical Takeaways
- •SDMA immunoassay can be reliably used in equine practice for assessing kidney function; the validated test correlates well with gold-standard LC-MS methodology
- •Unlike in small animals, sex and breed do have minor effects on SDMA in horses—Clydesdales show slightly higher values—so breed-specific reference ranges may be useful
- •For draft horse practitioners, SDMA offers a more sensitive GFR indicator than creatinine alone and is not confounded by muscle mass differences, making it useful for early renal disease detection across different draft breeds
Key Findings
- •SDMA immunoassay for equine serum was validated with strong correlation to LC-MS (R = 0.74, P < 0.001)
- •SDMA was significantly lower in Percherons and Belgians compared to Clydesdales, but all medians remained <14 μg/dL
- •SDMA and creatinine were moderately correlated (R = 0.60-0.66, P < 0.001) and both showed no differences between sexes or correlation with age
- •Reference range for healthy draft horses: SDMA 9.7 [9.5-10.0] μg/dL and creatinine 1.3-1.4 mg/dL across breeds