Sysmex Norge

More than error correction


Because nucleated red blood cells (NRBC) have a size and a nucleus similar to that of lymphocytes, many haematology analysers misclassify NRBC and produce a wrong total leukocyte and lymphocyte count.

Usually such samples are flagged for microscopic analysis. You then have to count the NRBC in the blood film manually and mathematically correct the total leukocyte and lymphocyte count. This is a costly, tedious and error-prone procedure. In addition, if the sample is not flagged, the NRBC may remain undetected and the total leukocyte 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 correcting the total leukocyte and lymphocyte count.

NRBC are seen as a reflection of extreme increases in erythropoietic activity, such as in 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 correlated with the severity of the disease. It has been observed that the entity and duration of the presence of NRBC in peripheral blood is associated with a poor prognosis in several haematological and non-haematological diseases.

Where to use NRBC

The NRBC counts provided on many of our analysers are used frequently for new-borns and young infants. In those patients, NRBC can occur physiologically in high numbers - up to 100 NRBC/100 WBC are possible in premature babies - and are used to correct WBC numbers. It is useful especially in patients from the neonatology or paediatric department or patients from paediatric private practices.


NRBC counting is also useful for patients with severe anaemia, especially those with thalassaemia or sickle cell disease as they usually have high NRBC counts, too. The NRBC count is important for differential diagnosis and can support patient monitoring to determine transfusion needs.

NRBC counting is important for all patients from the intensive care unit as detecting NRBC can indicate an increased mortality risk, and for patients with any condition producing haematopoietic stress such as severe infection, hypoxia or massive acute haemorrhage. This too can lead to circulating NRBC.


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 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).

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

Immature Platelet Fraction

Reticulocyte haemoglobin
equivalent (RET-He)

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