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Normoblasts: not always normal
  1. R. Goggs, BVSc, DACVECC, PhD, MRCVS
  1. Cornell University Hospital for Animals, Ithaca, NY, 14850, USA
  1. e-mail: r.goggs{at}

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BIOMARKERS are all the rage in both human and veterinary medicine (Calfee and others 2008). Biomarkers may be defined as biological molecules found in blood, bodily fluids or tissues that can be objectively measured and evaluated as indicators of normal or pathological processes or pharmacological responses to therapeutic interventions (Naylor 2003). The ideal biomarker is a robust analyte that can be simply, cheaply and reliably measured; is sensitive and specific; and is predictive of outcome. Few, if any, biomarkers meet all of these criteria. An understanding of the origins and mechanisms that stimulate the production, release and degradation of any biomarker are necessary to maximise their usefulness and to evaluate their shortcomings.

Nucleated red blood cells (NRBCs), also called erythroblasts or normoblasts, are the penultimate prematuration stage of erythrocytes. The presence of NRBCs in circulation is most frequently seen in patients with strongly regenerative anaemia, where they are an indicator of the marrow response to erythropoietin. NRBCs typically have polychromatophilic or haemoglobinised cytoplasm and round nuclei. When NRBCs are part of a regenerative response, polychromasia, anisocytosis and anaemia are likely to also be present (Fig 1).

FIG 1:

Multiple normoblasts in the blood smear of a dog with immune-mediated haemolytic anaemia. Marked polychromasia and anisocytosis can also be seen

The presence of NRBCs in the absence of …

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