Predictive Prognosis Value of CRP Measurement and CAR in Dogs Infected with Parvovirus

Canine parvoviral (CPV) enteritis is frequently associated with systemic inflammatory response syndrome (SIRS), yet objective biomarkers for early detection remain limited. This study evaluated the diagnostic performance of C-reactive protein (CRP), albumin, and the CRP/albumin ratio (CAR) in 60 dogs (45 CPV-positive and 15 healthy controls). CRP and CAR were markedly higher in infected dogs, while albumin was significantly reduced (all <i>p</i> < 0.001). ROC analysis demonstrated excellent discrimination for SIRS, with AUC values of 0.87 for CRP and 0.86 for CAR and optimal ROC01 thresholds of 2.25 mg/dL and 1.23, respectively. The IDEXX CRP-based SIRS classification showed moderate agreement with the clinical reference (κ = 0.56), whereas a conditional inference tree and logistic regression models confirmed CRP as the most informative variable. The final age-adjusted model including the interaction age × CRP achieved superior performance (AUC = 0.93; κ = 0.84), indicating that CRP's predictive effect varied with age. These results demonstrate that CRP and CAR are complementary, accessible biomarkers for assessing systemic inflammation in CPV infection and suggest that the IDEXX CRP cut-off (>3 mg/dL) may be conservative, as values above 2.25 mg/dL already reflect clinically relevant inflammatory activity.