Frequency of Nucleated Red Blood Cells in the Peripheral Blood of ICU-Admitted Patients

Background Nucleated red blood cells (NRBCs) are not normally found in the peripheral blood of normal healthy individuals. The presence of NRBCs on an adult peripheral blood smear indicates that there is an extremely high demand for the bone marrow to manufacture RBCs and that immature red blood cells are being released into the bloodstream. Anemia, myelofibrosis, thalassemia, miliary tuberculosis, malignancies of the bone marrow (myelomas, leukemias, lymphomas), and prolonged hypoxemia are a few possible pathogenic reasons. Critically ill patients who have NRBCs have a high mortality rate and a worse prognosis. Objective: To evaluate the clinical significance of NRBCs in the peripheral blood of critically ill patients admitted to the ICU to find a cut-off to predict mortality. Materials and Methods: A cross-sectional study was carried out over a period of six months September 1, 2020, to March 31, 2021, in Lahore, Pakistan. A total of 800 critically ill patients of both sexes in the age group of 18-70 years were included. Patients younger than 18 years and patients who underwent surgery were excluded. A quantity of 3 ml of whole blood sample in an ethylenediamine tetraacetic acid (EDTA) vial from each patient was run on SYSMEX XN-9000 (Sysmex Corporation, Kobe, Hyogo, Japan) and the results were reviewed on peripheral smears. Results: The incidence of NRBCs in ICU-admitted patients was 62.5% (500/800). The total number of NRBC-positive patients recovering after the treatment was 364 (72.8%). The overall mortality of NRBC-positive patients was 30% (150/500). It was significantly higher (p<0.001) than that of NRBC-negative patients (14%; 44/300). During treatment, the highest mortality rate was seen in patients due to malignancy (100%), followed by sepsis (58.8%). It was observed that the disease pattern and number of NRBCs were significantly different (p<0.001) among all disease groups. However, there was no statistically significant difference in NRBCs on the basis of gender (p >0.05). In our study, a cutoff of NRBCs of 2.50 showed a high risk of mortality with a sensitivity of 91%. Conclusion: The presence of NRBCs may predict mortality in critically ill ICU-admitted patients. Their presence in the blood may be regarded as a marker of severity suggesting a high risk of ICU death.