Clinical significance of blood cell ratios in healthy and sick Leishmania infantum-seropositive dogs.

Background: The accuracy of blood cell ratios (BCRs) as cost-effective and easily accessible diagnostic and prognostic markers of inflammatory conditions has been investigated in veterinary medicine in recent years.

Methods: Neutrophil-to-lymphocyte (NLR), monocyte-to-lymphocyte (MLR), and platelet-to-lymphocyte (PLR) ratios were studied in 195 dogs clinically evaluated and tested for anti-Leishmania infantum (Li) antibodies (Li-seronegative (Li), n = 10; Li-seropositive clinically healthy (Li), n = 100; Li-seropositive with clinical and/or clinicopathological abnormalities (Li), n = 85). The Li dogs were classified in LeishVet stages IIa/IIb (Li) (n = 66) and III/IV (Li) (n = 19). BCR relationships with LeishVet clinical stage, antibody levels, and serum protein electrophoretic fraction concentrations were investigated.

Results: Higher NLR values were found in Li, Li, and Li sick dogs compared to Li dogs (P < 0.001). Higher NLR and MLR were found in Li (NLR, P < 0.001; MLR, P = 0.034) and Li dogs (NLR, P < 0.001; MLR, P = 0.005) compared to Li dogs, and in Li dogs (NLR, P = 0.002; MLR, P < 0.001) compared to Li. All three BCRs were higher in Li (NLR, MLR, P < 0.001; PLR, P = 0.023) and Li dogs (NLR P < 0.001; MLR P = 0.001; PLR, P = 0.012) compared to Li dogs. The BCRs failed to distinguish dogs with moderate (Li) and severe or very severe disease (Li). BCRs demonstrated weak positive correlations with serum globulin fractions and antibody levels, and weak negative correlations with serum albumin level were found. Li dogs presenting hypoalbuminemia showed higher MLR ratios (P = 0.001) than those with normal albumin values.

Conclusions: This study shows that BCR measures provide useful information for differentiating antibody-positive healthy and sick dogs at diagnosis. Dogs with hypoalbuminemia showed higher MLR values despite monocytosis being very rare.