What is anaemia?

Anaemia (also known as "low blood") is the name for the condition in which there is a low amount of red blood cells in the body. In healthy persons, new blood cells are continuously made in the bone marrow to replace those that have been destroyed though wear and tear from traveling through the blood vessels. When the number of red blood cells begins to drop, the kidneys make a chemical called erythropoietin (EPO), which acts as a signal to the bone marrow to produce more cells. Normal red blood cells are packed with a protein called hemoglobin, which binds oxygen from air in the lungs and releases it for use in the body. If you have too few red blood cells, the body tissues cannot carry out their normal functions.

What are its symptoms and signs?

Mild anaemia usually does not produce any symptoms. Severe anaemia may cause you to feel tired, dizzy, or short of breath; make the skin appear pale, especially under the nails or on the underside of the eyelids; and cause a rapid heart rate.

What causes anaemia?

Anaemia results from one or a combination of the following conditions:

1. Decreased red blood cell production by the bone marrow

* Vital nutrients, such as iron, vitamin B12, or folic acid, may not be available to the bone marrow. This may occur because of poor diet or problems with absorbing these nutrients from the gut.

* Medications often suppress the production of red blood cells. Examples of such drugs include trimethoprim-sulfamethoxazole (TMP-SMX, Bactrim, Septra), zidovudine (AZT), pyrimethamine, amphotericin B, alpha-interferon, and chemotherapy (anti-cancer) agents.

* Certain infections may interfere with red blood cell production or replace normal bone marrow tissue. Examples include severe bacterial infections, tuberculosis, Mycobacterium avium complex (MAC), or HIV itself.

* Tumors such as lymphoma may displace or destroy normal bone marrow tissue.

* Many acute and chronic diseases result in decreased production of EPO by the kidneys.

2. Blood loss from trauma, the gut, or the uterus

* Bleeding may be caused or worsened by inadequate levels of blood clotting elements, such as platelets (a condition called thrombocytopenia) or certain proteins (clotting factors) that are made in the liver.

3. Increased destruction of red blood cells

* Destruction may result from an inherited disorder, such as sickle cell disease, that causes red blood cells to be more fragile than normal. Some kinds of inherited red blood cell disorders (for example, glucose 6-phosphate dehydrogenase [G6PD] deficiency) only cause problems if taking certain drugs.

* Red blood cells may also be destroyed prematurely in the presence of an enlarged spleen.

How is anaemia diagnosed?

Diagnosing anaemia is easy, but finding its cause can be difficult in some cases. Doctors determine if anaemia if present by performing a blood test called a complete blood count (CBC), which measures the level of hemoglobin and the concentration of red blood cells (hematocrit) in your blood. While anaemia is unusual in patients with early HIV disease, it is very common in those with AIDS.

If your hematocrit is less than 30, the anaemia is considered moderate. If your hematocrit is less than 25, the anaemia is severe. Your doctor will generally order a CBC at least every 6 months if the T-cell count is below 500, and every 1-3 months if the count is below 200. A CBC should be performed right away if you have any symptoms of anaemia.

What type of evaluation is performed?

Evaluation of the cause of anaemia should include a careful review of all prescribed, over-the-counter, and alternative medications you are taking; a physical examination to look for signs of bleeding from the gut or uterus; a microscopic examination of cells from your blood (peripheral blood smear); and a test for bone marrow production (reticulocyte count). Other laboratory studies that are sometimes ordered include levels of iron, vitamin B12, and folic acid; hemoglobin electrophoresis and G6PD level; and an EPO level. If these tests do not reveal the cause of anaemia, a procedure to get a sample of bone marrow by inserting a large needle into a hip bone (bone marrow aspiration) may be necessary. Many patients find this procedure painful during the brief time when the needle is inserted into the bone.

How can anaemia be treated?

The best way to manage anaemia is to identify its cause and to treat the underlying condition. In some cases, testing does not determine a specific cause for anaemia, and in others, especially in patients with advanced HIV disease, the cause may be a condition that is difficult or impossible to treat. In these instances, if the EPO level is low, giving supplemental EPO by injection may improve the anaemia and make red blood cell transfusion unnecessary or less frequent. In other cases it may be necessary to give blood cell transfusions periodically, especially if the hematocrit is 25 or below. However, transfusions have some risks, including the transmission of infections such as hepatitis, and are expensive.

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