RESEARCH COMMUNICATIONS OF THE 28th ECVIM-CA CONGRESS

Kidney disease is common in companion animals, and traditionally diagnosed with serum creatinine concentration (sCr), blood urea nitrogen, and urine specific gravity. More recently, it has been demonstrated that the kidney biomarker Symmetric dimethylarginine (SDMA) correlates with glomerular filtration rate, increasing earlier than sCr with acute kidney injury and chronic kidney disease. This prospective study compared accuracy and precision of two commercial SDMA assays, the IDEXX SDMA® Test manufactured by IDEXX Laboratories, Inc. and the SDMA ELISA manufactured by DLD Diagnostika, GmbH. Accuracy and precision for both commercial assays was measured relative to the established reference method, liquid chromatography/mass spectrometry (LC‐MS). Anonymized surplus canine and feline serum samples submitted to an IDEXX commercial reference laboratory were used in this study. Thirty canine and 30 feline serum samples were used to evaluate accuracy compared to LC‐MS. Pooled canine samples with a low SDMA concentration and pooled feline samples with a high SDMA concentration were used to evaluate precision. Using a best fit linear model, the IDEXX SDMA® Test resulted in a slope of 1.06 and an intercept of 0.23, with R2 = 0.99, and the DLD SDMA ELISA resulted in a slope of 0.38 and an intercept of 11.23, with R2 = 0.27. Estimated bias over a clinically relevant range for SDMA (10 – 45 μg/dL) was 1‐3μg/dL for the IDEXX SDMA® Test, while the DLD SDMA ELISA showed considerable bias, 5 to ‐17μg/dL. Day‐to‐day precision analysis of the low SDMA concentration samples showed 7.7% total coefficient of variation (CV) for the IDEXX SDMA® Test and 31.1% for the DLD SDMA ELISA. For the high SDMA concentration samples, total CV was 2.3% for the IDEXX SDMA® Test and 28.2% for the DLD SDMA ELISA. In this study the IDEXX SDMA® Test was more accurate and more precise than the DLD SDMA ELISA when compared to the reference method of LC‐MS, supporting the conclusion that the IDEXX SDMA® Test is more suitable for clinical use in the diagnosis and monitoring of kidney disease in dogs and cats.