Reticulocytes are the newly made, somewhat immature red blood cells that are released into the bloodstream. The reticulocyte count aids the doctor in measuring the amount or percentage of the new red blood cells. The count reflects the quality of bone marrow function in the body. Red blood cells are made by the bone marrow. In the bone marrow, blood-forming stem cells differentiate and develop into reticulocytes which further develop into red blood cells (RBC)
. Reticulocytes are minimally larger than mature red blood cells. Mature red blood cells have no nucleus, but reticulocytes have some strands of RNA, a genetic material. When they become fully mature, they lose the RNA. They fully mature one or two days after they have been released by the bone marrow into the bloodstream. The reticulocyte count reflects the ability of the bone marrow to perform its function optimally – it indicates whether it is producing an adequate amount of red blood cells or not. Red blood cells have a lifespan of 120 days in circulation. The bone marrow's job is to constantly reproduce and replenish red blood cells, which age, degrade, or are lost through bleeding. In a healthy individual, a stable number of red blood cells are maintained in the bloodstream through continual replenishment. The production of red blood cells is detrimentally impacted by a number of conditions and diseases. Their survival is also contingent on these. Some conditions may also lead to heavy bleeding. These conditions may also cause an increase or decrease in the number of red blood cells, and it may also impact the reticulocyte count. The test is used by the doctor to evaluate bone marrow function. Low or high reticulocyte count indicates something awry in bone marrow function. When an individual experiences acute or chronic bleeding, or hemolysis (red blood cell destruction), it can lead to fewer red blood cells in the blood, resulting in anemia. In this situation, the body reacts by increasing the rate of red blood cell production and releasing a steady flow of slightly immature red blood cells sooner into the bloodstream. Therefore, the number and percentage of reticulocytes in the blood increases until the adequate number of red blood cells replaces the ones that were lost. On the other hand, lower reticulocyte counts occur when the bone marrow fails to function properly. This can happen due to a bone marrow disorder like aplastic anemia. It can also happen due to occurrences like cirrhosis of the liver, kidney diseases, radiation, chemotherapy, or deficiencies in nutrients like iron, folate, or vitamin B12. Less production of reticulocyte counts can lead to fewer red blood cells in circulation, less hemoglobin
which leads to less oxygen-carrying capacity, a lower number of red blood cells in the blood overall, and a low number of new red blood cells when the old ones are not replenished. Sometimes, the reticulocyte count and the red blood cell count may be higher than normal because of the production of red blood cells in excess by the bone marrow. This can be due to erythropoietin
or other chronic disorders.