First automated immunoassay for symmetric dimethylarginine (SDMA) with reference interval establishment

The measurement of kidney function is critical for early detection and management of acute kidney injury and chronic kidney disease. Traditional biomarkers such as creatinine and cystatin C are commonly used but have significant limitations due to factors such as muscle mass, diet, hydration, and extrarenal conditions. Creatinine-based equations have raised concerns over health equity regarding racial differences in estimates of kidney function. In response, symmetric dimethylarginine (SDMA) has emerged as a promising biomarker due to its reduced sensitivity to muscle mass and other extrarenal variables. However, the clinical adoption of SDMA has been limited by the need for more efficient, automated testing methods. This study aimed to evaluate the first fully automated immunoassay for SDMA and compare its performance to the gold-standard liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. We also established reference intervals using over five hundred samples from the Association for Diagnostics and Laboratory Medicine (formerly AACC) sample bank. Our results demonstrate that the automated IDEXX SDMA® immunoassay provides rapid, accurate, and reliable measurements, offering significant potential to introduce this biomarker to the clinical space to aid in diagnosing and treating kidney dysfunction.