Medical Director, Research & Development Antech/MARS Petcare Science & Diagnostics Loveland, Colorado, United States
Abstract:
Background: SDMA (symmetric dimethylarginine) is a renal biomarker that reflects glomerular filtration rate (GFR) and is used for the detection and monitoring of renal disease. An in-house assay can provide rapid SDMA test results which can facilitate diagnosis and early treatment interventions. Hypothesis/
Objectives: The Antech Element i+™ SDMA immunoassay (Antech Diagnostics, Mars Petcare Science & Diagnostics) will show acceptable bias, precision, reproducibility and low interference. Animals: Dog and cat serum and lithium heparin plasma samples with SDMA concentrations spanning the reportable range.
Methods: Prospective method comparison study. Dog (n=188) and cat (n=177) samples spanning the reportable range (7-80 µg/dL) were tested on both reference method and Element i+™. Precision was performed over 15 days with 2 runs/day in triplicate. Reproducibility was conducted over 5 days, with 5 replicates and 3 instruments for repeatability and between-laboratory reproducibility. Interference testing was performed with 5 common exogeneous substances. Cross-reactivity was evaluated with 3 structural analogs. Statistical analyses included regression (Passing-Bablok/Deming), scatter/difference plots, and estimation of bias.
Results: Regression analysis reported excellent correlation for both species (cat R=0.9; dog R=0.9) and there was minimal proportional bias (cat slope =0.99 [95% CI:1.06-0.94]; dog slope =0.98 [95% CI:1.07-0.90]) . The coefficient of variation (CV) was < 15% for both precision and reproducibility . Interfering substances produced < 15% change versus controls. Cross-reactivity produced < 2% change versus controls. Conclusions and Clinical Importance: The Element i+™ SDMA immunoassay demonstrated acceptable accuracy, precision, reproducibility, and minimal interference, supporting in-clinic renal function assessment in dogs and cats.
