They are produced primarily in the bone marrow and are only occasionally observed in peripheral blood.
Nucleated RBCs (NRBC, normoblasts) are a very immature form of RBCs seen when there is a severe demand for RBCs to be released by the bone marrow or marrow involvement by fibrosis (=development of fibrous connective tissue as a reparative response to injury or damage) or a tumor.
In healthy adult patients the NRBC count on a should be zero.
In those who are not in perfect health, the most important benefit of an NRBC count is to exclude a false high in the WBC count. Size-wise nucleated red blood cells are similar to lymphocytes. Because of that, many laboratory analyzers mislabel them and hence list a wrong lymphocyte and total white blood cell (WBC) count.
A NRBC count should also be performed routinely for all pediatric (=medical care of infants) and neonatal samples.
- Prognostic value of nucleated red blood cells in critically ill children, https://www.ncbi.nlm.nih.gov/pubmed/24706413
Nucleated red blood cells in the fetus and newborn, https://fn.bmj.com/content/84/3/F211
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