Negative correlation between serial changes in the reticulocyte number and C-reactive protein level in dogs with delayed reticulocytosis.

Inflammation suppresses erythropoiesis, leading to non-regenerative anemia in dogs. Currently, clinical evidence of this inhibitory effect remains limited. This study provides important clinical insight by demonstrating a negative correlation between C-reactive protein (CRP) concentration and reticulocyte count over time in dogs with inflammatory anemia. This study aimed to leverage inflammatory anemia as a model to examine the longitudinal relationship between CRP levels and reticulocyte counts in dogs. Medical records of 23 dogs diagnosed with various inflammatory conditions and persistently non-regenerative erythropoiesis were retrospectively reviewed. Serial results of hematological and serological parameters were analyzed using linear mixed-effects models to account for intra- and inter-individual variation. Reticulocyte counts in anemic dogs with resolving underlying inflammatory conditions were significantly negatively correlated with CRP levels (standardized β=-0.53, 95% confidence interval (CI) -0.68 to -0.37; P<0.001). Moreover, cross-sectional analysis revealed that higher CRP levels were significantly associated with lower reticulocyte counts, suggesting that the severity of inflammation may be linked to reduced reticulocyte counts (Pearson's r=-0.5; P=0.01). Similarly, erythropoietic responses to darbepoetin alfa appeared to be attenuated in dogs with elevated CRP concentrations. In these dogs, whose mean CRP concentration was 6.15 mg/dL, the onset of reticulocytosis was delayed approximately twofold, and the increase in peak reticulocyte count was approximately 38% lower than that in dogs with normal CRP concentrations. This study provides clinical evidence supporting an association between systemic inflammation and reduced or delayed reticulocytosis in dogs, highlighting the clinical utility of concurrently monitoring CRP and reticulocyte levels to assess disease progression and inflammatory recovery.