Reticulocyte count

Other names: Reticulocyte Index; Retic Count; Corrected Reticulocyte

Reticulocytes are immature red blood cells, which are produced in the bone marrow. Most of the red blood cells released into the bloodstream are mature cells; however, around 0.5-2% of the red blood cells in the bloodstream will be reticulocytes. The test is used to measure the number of reticulocytes in the blood; it can be used as a marker for bone marrow function.

Red blood cells usually survive for around 120 days and the body constantly replenishes the stock of red blood cells; this is done in the bone marrow. If the production of new cells is disturbed, this may lead to a decrease in the number of red blood cells in the bloodstream and this contributes to anaemia.

When is the test used?

The test is done to assess the function of the bone marrow and to check that enough red blood cells are being produced. The test is also used to distinguish between different types of anaemia; other blood tests are usually ordered if the doctor suspects that a patient has anaemia. The test is usually carried out as part of a series of tests which make up the full blood count.

The reticulocyte test is usually ordered when the results of other blood tests show that the patient has a low red blood cell count; it is also ordered when the patient has symptoms of anaemia, including pale skin, tiredness, lethargy, weakness, breathing difficulties and blood in the stools.

The test may also be ordered when a patient has iron or vitamin B12 or folate deficiencies.

How is the test done?

The test is done by taking a sample of blood from the patient’s arm; a needle is inserted into a vein (usually on the inside of the elbow) and the blood is drawn out into a syringe. Once the sample has been collected, the blood will be placed in a sample bottle, labelled with the patients name and sent for testing at the laboratory.

If the patient is a very small child or baby, the sample will be collected from their heel; a needle will be used to prick the heel and the blood will be collected and analysed.

What do the test results show?

The test results should give the doctor an idea of how effectively the patient’s bone marrow is working; in order to evaluate the results, a calculation is done to measure the corrected reticulocyte count or the reticulocyte index.

An increased reticulocyte percentage may indicate that patient has iron deficiency anaemia, haemolytic anaemia, aplastic anaemia or pernicious anaemia; raised levels may also be associated with haemorrhages and radiation therapy.

Specific Blood Tests

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