Analytical comparison of three canine C-reactive protein assays in clinical use in Japan.

Abstract

C-reactive protein (CRP) is a key biomarker for diagnosis and prognosis in dogs. Accurate and consistent CRP measurements are essential for clinical decision-making. In Japan, different CRP measurement systems are commonly used, but their compatibility has not been validated. In this study, we evaluated the correlation and agreement among three CRP assay systems (immunonephelometry, immunoturbidimetry, and dry chemistry) using 138 dog plasma samples. Strong correlations (r >0.9) were observed, but regression analysis and Bland-Altman plots revealed systematic errors, indicating that these systems are not interchangeable. These findings highlight the need for system-specific reference ranges and clinical decision thresholds and suggest that a common calibration agent could enhance comparability and support the standardization of CRP measurements in veterinary medicine.