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Nucleated red blood cells – NRBC

More than error correction

Why count NRBCs?

Nucleated red blood cells (NRBC) have a size and nucleus similar to that of lymphocytes. As a result, many haematology analysers misclassify NRBC and produce a wrong total white blood cell (WBC) and lymphocyte count. Usually flagged for microscopic analysis, you now have to count the NRBC in the blood film manually and mathematically correct the total white blood cell and lymphocyte count. This is a costly, tedious and error-prone procedure.

That’s the positive scenario. If the sample is not flagged, the NRBC may remain undetected and the total white blood cell and the lymphocyte count may be wrongly elevated. Many still think automated NRBC measurement is no more than a way of correcting these counts. Yet the clinical value of measuring NRBC goes far beyond error correction.

NRBC counts have an important clinical value

NRBCs are seen as a reflection of extreme increases in erythropoietic activity. Perhaps acute haemolytic episodes and severe hypoxic stress, or as a result of a haematological malignancy. This includes many leukaemias and myelodysplastic syndromes, and some kinds of lymphoma.
NRBC can also be present in thalassaemia syndromes, bone marrow metastases of solid tumours, extramedullary haematopoiesis and other conditions of haematopoietic stress such as sepsis, or massive haemorrhages. In these situations, their presence is highly correlated with the severity of the disease. It has been observed that the entity and duration of the presence of NRBCs in peripheral blood is associated with a poor prognosis in several haematological and non-haematological diseases.

Sysmex’s NRBC count is reliable

Sysmex’s analysers provide a sophisticated NRBC count that is accurate for both high and low counts. This accuracy is needed because:

  • In neonate blood samples and others with high NRBC counts the WBC count needs to be corrected
  • In adult blood samples even a very low NRBC count can be meaningful.


Since we use a separate reagent for NRBC detection, we actually count the cells instead of estimating them. The NRBC count is fast and inexpensive and on our flagship XN analysers is included in every measurement. On our X-Class analysers it is performed when needed. NRBC are reported in % (per 100 WBC) and # (per µL).

Who benefits from using NRBC?

  • Patients from the neonatology or paediatric departments or from private paediatric practices


NRBC counts are used frequently for newborns and young infants. In those patients, NRBCs can occur physiologically in high numbers - up to 100 NRBC/100 WBC are possible in premature babies - and are used to correct WBC numbers.

  • Patients with severe anaemia/transfusion needs


Patients with thalassaemia or sickle cell disease benefit especially from NRBC monitoring as they usually have high NRBC counts. The NRBC count is important for differential diagnosis and can support patient monitoring to determine transfusion needs.

  • All ICU patients


Detecting NRBC can indicate an increased mortality risk as described above. It is an indicator of patients with any condition producing haematopoietic stress, such as severe infection, hypoxia or massive acute haemorrhage, as this too can lead to circulating NRBC.

Using NRBC in routine

In healthy adult patients, the automated NRBC count on a haematology analyser 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. This could lead to an incorrect diagnosis and treatment, especially in neonatal patients with sepsis and low WBC counts. Additionally, an NRBC count should be included routinely for all paediatric and neonatal samples. It is strongly recommended for severely diseased adult patients as it can indicate whether patients need special attention and treatment.

Immature Granulocyte
(IG)

Immature Platelet Fraction
(IPF# and %)

Reticulocyte haemoglobin
equivalent (RET-He)

Neutrophil Granularity
and Reactivity
(NEUT-GI, NEUT-RI)

Hypochromic and Hyperchromic
Red Blood Cells
(HYPO-He, HYPER-He)

Microcytic and Macrocytic
Red Blood Cells
(MicroR, MacroR)

Reactive and Antibody-
synthesizing Lymphocytes
(RE-LYMP, AS-LYMP)

Fragmented
red blood cells (FRC*)

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