Abstract / Summary
Serum protein capillary electrophoresis can characterise dysproteinaemia in dogs tested for canine leishmaniosis (CanL) as an integrated clinicopathological phenotype of humoral immune activation. This retrospective laboratory-based study evaluated serum protein electrophoretic patterns in 5544 dogs tested for CanL in Portugal between 2009 and 2026. Anti-Leishmania antibody results were classified into five ordered categories: negative, inconclusive, low positive, positive/high positive and very high positive. Total protein, albumin, alpha-1, alpha-2, beta and gamma fractions, albumin-to-globulin and albumin-to-gamma-globulin ratios were analysed. A separately defined reference subpopulation of 254 clinically healthy seronegative dogs aged ≥ 1 to <4 years was used to establish study-specific non-parametric 95% reference intervals. After excluding inconclusive results, binary analysis included 2454 seronegative and 2910 seropositive dogs. Seropositive dogs had higher median gamma globulins than seronegative dogs (1.5 vs. 0.8 g/dL; p < 0.001), with lower albumin-to-globulin (0.7 vs. 1.0; p < 0.001) and albumin-to-gamma-globulin ratios (1.9 vs. 4.2; p < 0.001). Across the ordinal serological scale, gamma globulins increased from 0.8 to 2.1 g/dL (p < 0.001), whereas the albumin-to-gamma-globulin ratio decreased from 4.2 to 1.2. Gamma globulins showed the strongest ordinal association (ρ = 0.522; p < 0.001) and moderate single-marker discrimination of seropositivity (area under the receiver operating characteristic curve = 0.768; 95% confidence interval: 0.755–0.780). These findings define the CanL proteinogram as a progressive, quantifiable immunopathological phenotype, dominated by gamma-region expansion and reciprocal albumin decline, supporting serum protein electrophoresis as a reference tool for interpretation and monitoring.