Performance evaluation of a canine C-reactive protein flow-immunosensor measurement system for clinical application

We investigated the analytical performance and robustness of a flow-type immunosensor (FIS)-based canine C-reactive protein (CRP) measurement system against analytical interferents. To improve the clinical applicability of the canine FIS CRP measurement system, we reduced the measurement time to 9 min. Statistical analyses, including scatter plots, Bland-Altman plots, and Passing-Bablok regression analyses, were performed to evaluate agreement with a comparative method (particle-enhanced turbidimetric immunoassay). Within-run imprecision (10 replicates) was 8.2% and 6.4% at ~39 and 115 mg/L; between-run imprecision (20 measurement days) was 9.9% and 6.5% at ~39 and 115 mg/L, respectively. The lower limit of quantification in the FIS measurement system was 4.0 mg/L, and quantification linearity was confirmed from 4.0 to 300 mg/L. CRP content was measured in canine heparinized plasma samples (n = 43) using both the comparative method (x) and the FIS (y). The regression equation for our new method (y) as a function of the reference method (x) was y = 0.979x + 0.592 (R² = 0.974). The system was robust against typical interfering components, including hemoglobin, lipids, and bilirubin. The FIS method was not suitable for K₂EDTA plasma. Based on between-run imprecision (20 measurement days) and concentration-specific targeted bias derived from Passing-Bablok regression, the observed total error was 20.3% and 14.6% at ~39 and 115 mg/L, respectively, meeting the American Society for Veterinary Clinical Pathology desirable and minimum performance goals, as well as optimal performance at the higher concentration level.