Retrospective investigation of the reticulocyte hemoglobin content in the dog

Reticulocyte hemoglobin content (RETIC-HGB) as part of complete blood count (CBC) in dogs is considered as an early diagnostic marker of iron deficiency. [1,2] A retrospective evaluation of the RETIC-HGB and the relation with the main parameters of the CBC was carried out in samples managed at the Veterinary Teaching Hospital, Clinical Pathology Laboratory. In addition, the trend monitoring of RETIC-HGB values in few patients and its comparison with the main markers of inflammation was done. All CBCs (Procyte, IDEXX®) performed from May 2018-January 2019 were collected and divided into 2 groups according to the RETIC-HGB values: <22.3 pg (RHr) and >22.3 pg (RHn). The main RBC and RETIC variables (HCT, MCV, MCH, MCHC, RETIC absolute value and RETIC-HGB) of the two groups were compared by Mann-Whitney or Chi-Square tests, and also the Spearman test (rho) was used to investigate their correlation. Six sick patients were monitored over time for RETIC-HGB, MCV, neutrophilia, C-Reactive Protein, and Fibrinogen. CBCs with reduced RHr were 21.5% (262/1,218). CBCs with RHr had significantly lower HCT and MCV values than CBCs with RHn (P=0.0001). Significant differences between the two groups for all the RBC and RETIC variables were also found. Anemia was observed in CBCs with RHn (23.9%; 229/956) and in CBCs with RHr (40.5%; 106/262). Normocytic normochromic anemia was assessed in CBCs with RHn (69.9%; 160/229) and in CBCs with RHr (52.8%; 56/106) (P=0.0036). Microcytic normochromic anemia was assessed in CBCs with RHn (17.0%; 39/229) and in CBCs with RHr (31.1%; 33/106) (P=0.0054). In both groups the most represented anemia was non-regenerative [RHn 71.6% (164/229), RHr 50% (53/106) (P=0.0002)] or moderately regenerative [RHn 4.8% (11/229), RHr 13.2% (14/106) (P = 0.013)]. There was no correlation between the RHr and the RBC and RETIC variables studied (rho range between -0.01/+0.29). During the monitoring of six patients the reduction of RETIC-HGB values was observed when there was neutrophilia and/or an increase in C-reactive protein and/or fibrinogen. CBCs with RHr values showed higher rate of occurrence and more severe form of anemia. [1] The clinical condition of dogs related to the CBCs collected was unavailable as well as parameters related to inflammatory markers inducing a study limitation except for 6 patients monitored over the time. In our study the reduction of RETIC-HGB was unable to indicate iron deficiency sooner than the reduction of MCV or MCHC. In accordance with previous studies, RETIC-HGB values appear to be influenced by inflammatory conditions in both anemic and non-anemic dogs. [3] [1] Nickel et al. Canine reticulocyte hemoglobin content (RET-H e ) in different types of iron-deficient erythropoiesis, Vet Clin Pathol, 46:422-429, 2017. [2] Fuchs et al. Evaluation of reticulocyte hemoglobin content (RET-He) in the diagnosis of iron-deficient erythropoiesis in dogs, Vet Clin Pathol, 46:558-568, 2017. [3] Meléndez-Lazo et al. Evaluation of the relationship between selected reticulocyte parameters and inflammation determined by plasma C reactive protein in dogs, J Comp Pathol, 152:304-312, 2015.