CD4 and viral load testing
Once you have tested positive for HIV, your doctor will do blood tests to determine your CD4 count and viral load as well as genotypic profile. Monitoring your CD4 count and viral load will help your doctor decide when you should start treatment. CD4+ lymphocytes are types of white blood cells that make up part of your immune system. These cells help protect and defend the body from viruses and germs. HIV gradually wipes out these cells and makes you more vulnerable to infections and illness.
People with healthy immune systems have a CD4 count that ranges between 800 to 1,300 cells per microlitre of blood. If you have HIV, your CD4 count falls dramatically during the first few months of being infected, and stabilizes after about 3 to 6 months. Without treatment though, your CD4 count will continue to decline. As your CD4 count goes down, your risk of getting sick goes up. A count below 200 cells per microlitre of blood means that your immune system is very weak and you are less able to fight certain infections (called opportunistic).
Your viral load is the amount of HIV virus in your blood (also called the number of copies of HIV RNA). Your viral load tells you how quickly the virus is replicating. At the beginning of HIV infection, your viral load increases quickly, but it will drop after some time even without treatment and stabilize to a consistent level (called set point). The higher the viral load, the more contagious the infection is and the faster the infection is likely to worsen. Treatment can help lower the viral load to very low or undetectable levels. However, inactive HIV is still present and will start replicating again if treatment is stopped. Viral load levels can range between undetectable to over a million copies. Your viral load should decrease with treatment but if it continues to increase that means the HIV has either developed a resistance to the treatment or you are not taking medicines properly, or both.
