Reticulocytes are immature red blood cells. A reticulocyte count (also known as a retic count, reticulocyte index, or corrected reticulocyte) is a measurement and percentage of how many reticulocytes are in the blood. This count indicates whether enough red blood cells are being produced in the bone marrow.
If the red blood cell count is either too low or too high, the body will attempt to maintain balance by producing and releasing either more or less reticulocytes. Your doctor can tell whether your body is creating and releasing these red blood cells properly by assessing how many red blood cells are in the blood.
Too few red blood cells, either from acute or chronic bleeding, can lead to anemia. Too many red blood cells could be a sign of bone marrow disorders or a vitamin deficiency. It could also be a result of radiation or chemotherapy. While the reticulocyte count does not diagnose anything, it is the first step to identifying where the issue is stemming from.
Most commonly, your doctor will recommend a reticulocyte count if he or she wants to assess the functioning of your bone marrow, or to see if the marrow is producing enough red blood cells. Another reason to do a reticulocyte count is to diagnose and distinguish between different types of anemia. Reticulocyte counts may also be used to help monitor progress after chemotherapy, bone marrow transplants, or after treatment for iron deficiency anemia.
Before the Test
Reticulocytes are counted through a blood draw. The process of taking a blood sample for testing is called venipuncture. You may need to fast (refrain from eating or drinking) for a specific period before the blood test. Ask your doctor about any specific pre-test considerations.
During the test, your doctor will take blood from a vein, usually from the inner elbow or back of the hand. First, your doctor will sterilize the area with an antiseptic. Then, he or she will wrap a plastic band around your arm to apply pressure and to help the vein swell with blood.
Once the vein swells, your doctor will insert a sterile needle directly into the vein. The blood will collect into an attached vial. Once enough blood has been collected for the sample, the plastic band is untied and the needle is removed from the vein. The site of the needle insertion will be cleaned and bandaged, if necessary.
Some individuals experience only slight pain from the needle prick, while others may feel moderate pain, especially if the vein is difficult to locate. It is common for the spot to throb after the procedure. Some bleeding is also common, as the needle will break the skin. For most people, bleeding is slight and will not cause any issues.
Infants and Young Children
For infants or young children, the testing process may be different. The doctor may instead make a small cut to allow blood to come to the surface. A test strip or slide will then be used to collect a small sample of blood. The area will be cleaned and bandaged if necessary.
Alternative Testing Methods
In some cases, a simple finger prick will suffice for blood testing. In this case, your finger will be pricked with a needle. When the blood comes to the surface, your doctor will collect a sample and then clean and bandage the finger.
Normal levels of reticulocytes vary due to differing laboratory procedures and levels of hemoglobin in the blood, which could change slightly due to bleeding. Pregnancy and living in high altitudes may also alter the amount of reticulocytes in the blood. Your doctor is looking for a stable percentage and number of reticulocytes in the blood. He or she can then assess the bone marrow functioning from this percentage.
High reticulocyte levels could indicate:
- acute bleeding
- chronic blood loss
- hemolytic anemia
- kidney disease
- Erythroblastosis fetalis, also called hemolytic disease (a potentially fatal blood disorder in a fetus or newborn)
Low reticulocyte levels could indicate:
- iron deficiency anemia
- folic acid deficiency
- aplastic anemia
- radiation therapy
- cirrhosis of the liver
- kidney disease
- vitamin B12 deficiency
- bone marrow failure (caused by drug toxicity, an infection, or cancer)
More tests may be administered to determine if reticulocyte count is considered abnormal.