What are Nucleated red blood cell (NRBC)?

Nucleated red blood cells (metarubricytes) represent the early stages of a red blood cell before it matures.

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.

Hematopoiesis_(human)_diagram_en — By original: User:A. Rad, svg file drawn with FlashMX by birdyderivative work: RexxS (Hematopoiesis_(human)_diagram.svg) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/) or GFDL (http://www.gnu.org/copyleft/fdl.html)%5D, via Wikimedia Commons

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.

Resources:

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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