Nucleated Red Blood Cells (nRBC)

Nucleated erythrocytes in blood in a case of canine plumbism. The PCV was 39%.

Nucleated red blood cells can be seen in peripheral blood (called a normoblastosis or erythroblastosis) under the following situations:

  • Regenerative anemia: In this case, the nRBCs will be accompanied by polychromasia or a reticulocytosis.
  • Bone marrow injury, e.g. endotoxemia, lead poisoning (plumbism)
  • Bone marrow neoplasia, e.g. primary myelodysplasia, acute myeloid leukemia
  • Extramedullary hematopoiesis
  • Altered splenic function, e.g. splenectomy, splenic hemangiosarcoma
  • Normal finding in some animals: Healthy alpacas can have low numbers of nRBCs (0-3/100 WBC). In some breeds of dogs, e.g. Miniature Schnauzers and Dachschunds, small numbers of nRBCs may be seen in the circulation of healthy animals.

nRBCs are counted (regardless of technique, i.e. manual or automated) as white blood cells (WBC). For this reason, the obtained "WBC" count (from an analyzer or a hemocytometer) is actually a nucleated count which includes WBC and nRBC. The obtained nucleated count must be corrected for the number of nRBC in the circulation. To correct the "WBC" or nucleated count, the number of nRBCs per 100 leukocytes is recorded during the differential leukocyte count when performing a blood smear examination. Then a correction is made as follows:

Corrected WBC = obtained nucleated cell count x (100 ÷ [nRBC + 100])

In reports from our laboratory, the WBC value with our routine hemograms is always a leukocyte count since we automatically correct for nRBCs (if more than 5 nRBC/100 WBC are counted). This correction is not performed with our automated hemograms (because the automated hemogram does not include a manual differential cell count). In most animals, the numbers of nRBCs are too low to significantly affect the WBC count, but in disorders where nRBCs are found in high numbers, e.g. lead poisoning, immune-mediated hemolytic anemia, the impact on the WBC count can be substantial.

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