For example, if your CD4 percentage is very different to your CD4 cell count, it might be a sign of another health problem. One circumstance when your doctor might measure your CD4 cell percentage could be if there is a big variation in your CD4 cell count between one test and the next. CD4 percentages are less likely to fluctuate than CD4 counts. You can also view our illustrated information about CD4 and viral load , the immune system , undetectable viral load and other tests.
CD4 count. Primary tabs View active tab Preview. Roger Pebody. May Key points CD4 cell counts give an indication of the health of your immune system.
The latest news and research on CD4 count. Glossary CD4 cell count A test that measures the number of CD4 cells in the blood, thus reflecting the state of the immune system. CD4 cells The primary white blood cells of the immune system, which signal to other immune system cells how and when to fight infections.
Next review date. This page was last reviewed in May This baseline test gives a picture of your immune system when you first enter into care. Later tests can be compared against this first result to see how things are changing over time and with treatment. It is important to get your CD4 count checked about every three to six months — or as often as your health care provider recommends. You will need more frequent CD4 cell tests if your count is low or falling, or if you are starting or changing treatment.
If you have been on HIV drugs for over two years, are virally suppressed and have a CD4 count over , your provider may suggest that you only need to get your CD4 count checked once a year. Many factors can affect your CD4 count, including the time of day, level of stress, your menstrual cycle, and infections such as the flu.
If you get a result back that surprises you or your health care provider, he or she will probably want you to get a second test. The second test would confirm any unexpected results or show that the first test's results were random — the result of lab error or an unimportant occurrence.
Try not to worry too much about a single abnormal test result; trends over time are usually more important. In addition to your CD4 cell count, your health care provider will want to check your CD4 percentage. This number tells you what percent of your total lymphocytes a kind of white blood cell are CD4 cells. A normal CD4 cell percentage is about 30 to 60 percent. The CD4 percentage is sometimes a more reliable measurement than the CD4 count because it tends to change less between measurements.
While the CD4 percentage gives information about the health of your immune system, the CD4 count is the preferred measurement for determining whether your HIV disease is progressing. Currently, treatment guidelines for adults are based on CD4 counts and not on CD4 percentage. A CD4 count can help your health care provider find out if you are at risk for serious complications from HIV.
The test can also check to see how well HIV medicines are working. You may also need a CD4 count if you've had an organ transplant. Organ transplant patients take special medicines to make sure the immune system won't attack the new organ. For these patients, a low CD4 count is good, and means the medicine is working. You will probably be tested again every few months to see if your counts have changed since your first test. If you are being treated for HIV, your health care provider may order regular CD4 counts to see how well your medicines are working.
A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes. There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
The lower the absolute CD4 count, the weaker the immune response. The absolute CD4 count is measured by a simple blood test, the results of which are reported as the number of CD4 cells per cubic millimeter of blood. By contrast, immune-suppressed individuals with HIV have counts that are typically less than , depending on the stage of infection, while people with advanced HIV can have or fewer CD4 T-cells per cubic millimeter.
The CD4 percentage represents the percentage of total lymphocytes that are CD4 cells and is measured using the same blood test as that for the absolute CD4 count. Clearly, the higher the percentage, the more robust the immune response.
If your CD4 count is lower than you expect, the CD4 percentage can put it into better perspective by telling this whether this is an actual change or just a fluctuation. Typically, in advancing disease, as the immune system becomes exhausted, it is less able to produce T-cells to defend itself. The absolute CD4 count and CD4 percentage give your healthcare provider a snapshot of the health of your immune system, as well as the prognosis of your disease moving forward.
In its simplest form, we know that CD4 counts of less than place a person with HIV at risk of opportunistic infections. The CD4 percentage, meanwhile, takes into consideration the total number of lymphocytes and is somewhat more predictive of a person's immediate and long-term health. If, for example, the CD4 count is higher only because the total lymphocyte count is higher, we would still have a cause of concern about the patient's health.
If, on the other hand, the CD4 is lower as a result of a lower lymphocyte count, we could interpret outcomes differently.
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