Red blood cell (RBC) indices are part of the complete blood count (CBC) test. They are used to help diagnose the cause of anemia, a condition in which there are too few red blood cells.
The indices include:
- Average red blood cell size (MCV)
- Hemoglobin amount per red blood cell (MCH)
- The amount of hemoglobin relative to the size of the cell (hemoglobin concentration) per red blood cell (MCHC)
How is the Test Performed?
A blood sample is needed.
Preparation for the Test
No special preparation is necessary.
How the Test will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
Why is the Test Performed?
RBCs transport hemoglobin which, in turn, transports oxygen. The amount of oxygen tissues receive depends on the amount and function of RBCs and hemoglobin.
The MCV reflects the size of red blood cells. The MCH and MCHC reflect the hemoglobin content of red blood cells. These RBC measures are used to diagnose types of anemia.
Anemias are defined based on cell size (MCV) and amount of Hgb (MCH).
- MCV less than lower limit of normal: microcytic anemia
- MCV within normal range: normocytic anemia
- MCV greater than upper limit of normal: macrocytic anemia
- MCH less than lower limit of normal: hypochromic anemia
- MCH within normal range: normochromic anemia
- MCH greater than upper limit of normal: hyperchromic anemia
Normal Results for RBC indices
- MCV: 80 - 100 femtoliter
- MCH: 27 - 31 picograms/cell
- MCHC: 32 - 36 grams/deciliter
The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different samples. Talk to your doctor about the meaning of your specific test results.
What Abnormal Results Mean
This test is used to diagnose the cause of anemia. The following are the types of anemia and their causes:
- Normocytic/normochromic (NC/NC) anemia is caused by sudden blood loss, prosthetic heart valves, blood infection (sepsis), tumor, long-term disease, aplastic anemia, or deficiency of the hormone erythropoietin caused by kidney failure.
- Microcytic/hypochromic anemia is caused by iron deficiency, lead poisoning, blood disorder called thalassemia, or inflammation.
- Macrocytic/normochromic or hyperchromic anemia results from chemotherapy, folate deficiency, or vitamin B12 deficiency.
RBC indices Risks
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.
Other risks associated with having blood drawn are slight, but may include:
- Excessive bleeding
- Fainting or feeling light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Bunn HF. Approach to the anemias. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 161.
Hutchison RE, McPherson RA, Schexneider KI. Basic examination of blood and bone marrow. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 30.
|Review Date: 2/24/2014
Reviewed By: Todd Gersten, MD, Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.