Reticulocyte hemoglobin content does not differentiate true from functional iron deficiency in dogs

Background: True and functional iron deficiency can result in anemia. Current tests to assess iron status often do not allow differentiation between these entities, which can affect optimal treatment. Previous work suggested low reticulocyte hemoglobin content (CHr) may be an early indicator of iron deficiency. Objective: This study aimed to correlate several inflammation markers with CHr values in dogs. We hypothesize that dogs with low CHr values have hematologic and biochemical evidence of inflammation. Methods: Animals with CHr values below the reference interval were included in the low CHr group, while dogs with normal or increased CHr were included in the control group. HCT, MCV, CHr, reticulocyte mean cell volume (MCVr), concentrations of serum iron, C-reactive protein (CRP), ferritin, and ceruloplasmin, and total iron-binding capacity (TIBC), percent transferrin saturation (% sat), and total WBC, neutrophil, and monocyte counts were determined. Nonparametric tests were performed; median values and percentage of abnormalities between each group were compared. Results: Relative to control dogs, animals in the low CHr group had higher median values for CRP, ferritin, ceruloplasmin, and WBC concentration (P <= .05), and lower median values for HCT and MCV (P <= .0001). Higher frequencies of abnormalities for CRP, ferritin, WBC, neutrophil, and monocyte concentrations (P <= .02) were present in the low CHr group. Conclusions: Dogs with low CHr values often have evidence of inflammation, but low CHr did not reliably predict Fe deficiency. Additional diagnostic tests are needed to differentiate true and functional iron deficiency.