Nucleated red blood cells as a prognostic indicator in dogs with anemia

Franziska HollmannVera GeisenKatrin HartmannRene Doerfelt^*

• LMU Small Animal Clinic, Ludwig-Maximilians-Universität München, Munich, Bavaria, Germany

Background: In human medicine, nucleated red blood cells (NRBCs) in the peripheral blood have been associated with a poor prognosis and increased mortality in critically ill patients. In critically ill dogs, mortality was also significantly associated with high peripheral NRBC count.Objective: This study aimed to determine the presence of NRBCs in the peripheral blood of dogs with regenerative and non-regenerative anemia and to evaluate the prognostic relevance of NRBCs in anemic dogs. Furthermore, the correlation between NRBCs and other blood parameters was examined.Materials and Methods: Medical records of 254 anemic dogs hospitalized from November 2013 to June 2020 were retrospectively reviewed. Inclusion criteria were a hematocrit of <30%, a minimum age of 6 months, and the presence of a manual blood smear evaluation. Data were analyzed using Fisher's exact test, Mann-Whitney U test, Kruskal-Wallis test with Dunn's post-hoc multiple comparison test, and Spearman correlation. P-values <0.05 were considered significant.One hundred ninety-one of 254 patients had NRBCs in their blood smear. The absolute NRBC count was significantly higher in dogs with regenerative anemia [1,514/µl (92 -40,810/µl)] compared to dogs with non-regenerative anemia [220/µl (10 -5,260/µl); p <0.001]. NRBCs were more often present in dogs with regenerative anemia (141/167) than in dogs with non-regenerative anemia (35/62; p <0.001). The NRBC concentration was not different between surviving and nonsurviving dogs (p = 0.080). An increase or decrease of NRBCs during hospitalization was also not associated with outcome.Conclusions: NRBCs commonly appear in the peripheral blood of dogs with regenerative anemia. Their presence and quantity are not associated with survival.