What is a Reticulocyte Count?

The reticulocyte count is a type of blood test which evaluates the functions of the bone marrow and at what rate blood production takes place. It is also done to assess the response of the body in the treatment of some blood disorders like anemia. Reticulocytes are young or immature red blood cells usually present in the circulation in very small amounts, approximately about one to two percent. They are produced in the bone marrow and released in the circulation. After about one or two days, they mature into red blood cells, which have a lifespan of approximately 120 days in circulation.

An increase or decrease in the number or percentage of reticulocytes in the blood can point to a number of disorders inside the body. The term used for a high reticulocyte count is reticulocytosis. Reticulocytosis often indicates that the bone marrow is producing more red blood cells (RBC) as a response to a decrease in RBC in the circulatory system. This could be due to blood loss, the destruction of RBC in anemia, or exposure to high altitudes. Individuals living in high altitude areas often have higher reticulocyte counts as the body's way of adjusting to the low oxygen level.

A decrease in the reticulocyte count often indicates failure of the bone marrow to produce new red blood cells, as in cases of tumors and infections occurring in the bone marrow. Kidney disease can also decrease the reticulocyte count and red blood cell count. Other causes of low reticulocyte counts include iron deficiency, folate deficiency, and vitamin B12 deficiency. Radiation therapy also often affect RBC production in many patients, as it suppresses the functions of the bone marrow.

Physicians usually request a reticulocyte count as well as a complete blood count (CBC) in order to evaluate the response of the body in the treatment of iron deficiency anemia and vitamin B12 deficiency anemia. The rise in the reticulocyte count and other blood indexes usually indicates that the bone marrow is responding well to such treatment. After bone marrow transplants, a rise in reticulocyte counts is also an indication of a successful transplant.

There are no special preparations for a reticulocyte count test. A phlebotomist extracts an amount of blood from the arm of a patient to be tested. The blood is then processed in the laboratory for the reticulocyte count, and is either read manually by a qualified laboratory personnel or through an automated method.