Nucleated red blood cells in critically ill cats

ObjectivesThis study investigated the presence of nucleated red blood cells (NRBCs) in the circulation as a prognostic factor in critically ill cats.MethodsCritically ill cats were prospectively included over 11 months if they fulfilled at least 3/4 systemic inflammatory response syndrome (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 hospital. For manual microscopic NRBC count, 300 nucleated cells were examined and recorded as relative NRBC count (rNRBC). Absolute NRBC (aNRBC) numbers were calculated from those values: aNRBC = rNRBC × (white blood cell [WBC]/100).ResultsNRBCs, and most commonly metarubricytes, were detected in 25/94 critically ill cats. Primary underlying diseases were infectious (n = 10), neoplastic (n = 33), metabolic (n = 29), cardiovascular (n = 10), neurological (n = 5) and miscellaneous (n = 7). A positive correlation of absolute NRBCs with corrected WBCs (r = 0.448) was observed. After 28 days, 18 cats were still 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 × 10⁹/l (range 0.032-28.990) and did not differ between survivors and non-survivors. Anaemia was not associated with NRBCs. All but one of the six NRBC-positive cats on day 2 did not survive.Conclusions and relevanceNRBCs can be observed in the blood of critically ill cats; however, their occurrence did not have a prognostic value.