Nucleated red blood cells in the blood of medical intensive care patients indicate increased mortality risk: A retrospective study

INTRODUCTION: The presence of nucleated red blood cells (NRBC) in human blood is physiologic only in early embryonic life. Normally, the peripheral blood of healthy adults is free of NRBC. In critically ill patients, the appearance of NRBC may be associated with poor prognosis, possibly in response to endotoxemia or hypoxia. Many studies of neonates have linked NRBC to poor outcomes. A small number of studies done in Europe explored the relationship in adult patients between NRBC and prognosis, specifically end-organ failure and mortality. If this relationship exists, NRBC could be used as a cost-effective prognostic factor in decision-making by the critical care team for relocating a patient from the intensive care unit to a regular floor. The goal of this study therefore was to assess the relationship between NRBC and mortality in patients on an intensive care unit in an inner city community hospital. METHODS: This observational analytic cohort study retrospectively reviewed 594 consecutive medical intensive care patients for the presence of NRBC throughout their hospital stay and documented mortality. Daily CBC (complete blood count) with differential test was considered standard of care management in the ICU and includes presence of NRBC. Patients were defined as NRBC-positive when NRBC were detected in the blood at least once. Patients were followed until discharge from the hospital. RESULTS: The incidence of NRBC was 10.4% (62/594). Mean patient mortality was 25.9% (154/594). Mortality for NRBC positive patients was 77.4% (48/62) and for NRBC negative patients was 19.9% (106/532) (p < 0.001). As a prognostic factor for mortality, NRBC was 96.8% specific and 31.2% sensitive. The first appearance of NRBCs was noted less than 7 days prior to death, and most within 1 day. CONCLUSION: Presence of NRBC in critically ill patients is often indicative of high mortality within days. These findings suggest that, when a critical care team believes it possible to relocate a patient from the ICU to a regular floor, the absence of NRBC that patient's blood will support that decision, whereas its presence will strongly weigh against it. This is the first U.S. study to examine the significance of NRBC in the blood of critically ill patients. Further investigation should pursue the relationship between cause of death and presence of NRBC.