EXPRESS: Nucleated red blood cells in critically ill cats

Objective This study investigates the presence of NRBCs in the circulation as a prognostic factor in critically ill cats. Methods Critically ill cats were prospectively included over 11 months if they fulfilled at least 3/4 SIRS criteria or if their general condition was severely reduced. All cats underwent a physical examination and blood collection for haematological and clinical chemical parameters, including NRBCs at admission and during hospitalisation. Outcome was defined as survival to 28 days after discharge from the hospital. For manual microscopic NRBCs count, 300 nucleated cells were examined and recorded as relative NRBC count (rNRBC). Absolute NRBC (aNRBC) numbers were calculated from those values: aNRBC = rNRBC × (WBC/100). Results NRBCs, and most commonly metarubricytes, were detected in 25/94 critically ill cats. Underlying diseases were infectious (10), neoplastic (33), metabolic (29), cardiovascular (10), neurologic (5) and miscellaneous (7). A positive correlation of absolute NRBCs with corrected white blood cells (r = 0.448) was observed. After 28 days, 18 cats were alive and 76 cats did not survive. Mortality did not differ between NRBC-positive and NRBC-negative cats (p = 0.641). Absolute NRBC count was 0.382 G/l (0.032–28.990 G/l) and was not different between survivors and non-survivors. Anaemia was not associated with NRBCs. All but one of 6 on day 2 NRBC positive cats did not survive. Conclusion and relevance NRBCs can be observed in the blood of critically ill cats but their occurrence did not have a prognostic value.