| Subject | Contents |
| Definition | A test that measures the percentage of reticulocytes (slightly immature red blood cells) in blood. |
| Alternative Names | |
| How the test is performed | Adult or child: Blood is drawn from a vein ( venipuncture ), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (fill with blood). A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the tourniquet is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding . Infant or young child: The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding. A special stain can be used to identify reticulocytes, because they contain remnants of RNA. Fully mature red blood cells are terminally-differentiated cells lacking nuclei and nucleic acids. The number of reticulocytes in the blood is proportional to their rate of synthesis and release by the bone marrow. The body will respond to bleeding or hemolytic anemia (breakdown of red blood cells) by an increased rate of red blood cell synthesis under normal circumstances. A lower-than-normal percentage of reticulocyte is suggestive of a nutritional deficiency. |
| How to prepare for the test | Adults: No special preparation is necessary. Infants and children: The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:infant test or procedure preparation (birth to 1 year) toddler test or procedure preparation (1 to 3 years) preschooler test or procedure preparation (3 to 6 years) schoolage test or procedure preparation (6 to 12 years) adolescent test or procedure preparation (12 to 18 years) |
| How the test will feel | When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing. |
| Why the test is performed | To determine if red blood cells are being created in the bone marrow at an appropriate rate. |
| Normal Values | The normal range is 0.5% to 2%. The normal range is higher if there has been any blood loss or hemolysis. |
| What abnormal results mean | A greater-than-normal percentage of reticulocytes may indicate: erythroblastosis fetalishemolytic anemia post-hemorrhage ( bleeding ) kidney disease with increased erythropoietin production A lower-than-normal percentage of reticulocytes may indicate: bone marrow failure (for example, from toxicity, tumor , fibrosis, infection) cirrhosis of the liverfolate deficiency iron deficiency radiation therapyVitamin B12 deficiency kidney disease with decreased erythropoietin production Additional conditions under which the test may be performed: anemia of chronic diseasecongenital spherocytic anemiahemolytic anemia due to G6PD deficiencyidiopathic aplastic anemiaidiopathic autoimmune hemolytic anemiaimmune hemolytic anemiapernicious anemiasecondary aplastic anemiadrug-induced immune hemolytic anemia |
| What the risks are | excessive bleedingfainting or feeling light-headed hematoma (blood accumulating under the skin) infection (a slight risk any time the skin is broken) multiple punctures to locate veins |
| Special considerations | The reticulocyte count may be increased by pregnancy . Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others. |
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