Comparative analysis of Ella™ and Simoa™ immunoassays for neurofilament light chain quantification in bovine serum and CSF

Neurofilament light chain (NfL) is a neuron specific cytoskeletal protein released into cerebrospinal fluid (CSF) and blood following axonal injury, serving as a sensitive biomarker of neuroaxonal damage. Ultrasensitive immunoassays now permit reliable detection of NfL at very low concentrations, with Simoa™ and Ella™ being the most widely used platforms. Direct comparisons between these technologies remain limited, particularly in non human matrices. This study evaluated the analytical performance and agreement between Simoa™ and Ella™ platforms in CSF and serum samples from healthy cattle and bovine presenting neurological symptoms. In CSF, Passing–Bablok (PB) regression analysis indicated good agreement with no systematic or proportional bias. In serum, Simoa™ produced significantly lower serum NfL concentrations compared to Ella™, and PB regression revealed a proportional bias between methods. Overall, Ella™ showed a significantly lower coefficient of variation than Simoa™, indicating higher repeatability. In conclusion, both assays showed strong agreement in quantifying NfL in bovine CSF, whereas serum measurements might require platform-specific interpretation, especially when NfL is used as a minimally invasive biomarker of axonal injury in cattle.