Q: Last month I got to know that I am HIV infected. I consulted a doctor regarding the same. He conducted some tests and all reports were normal including TB. When I went for the next consultation, he asked me to get my CD4 count and viral load checked. My CD4 count is 259 cells/mcl. By knowing the CD4 count, can I know when I got infected with HIV?

A:The CD4 count reflects the strength of your immune system, how far HIV disease has advanced or the stage of the disease, and helps predict the risk of complications and infections. It cannot predict when you got infected. As done by your doctor, the CD4 count and a viral load test are ordered when a person is first diagnosed with HIV as part of a baseline measurement. Both tests should be repeated about 2-8 weeks after starting or changing anti-HIV therapy. If treatment is maintained, a CD4 count should be performed every 3-6 months thereafter. Normal CD4 count in adults range from 500 to 1,500 cells per mcl of blood. Generally, CD4 count decreases as HIV disease progresses. According to medical guidelines, medical treatment is started when an HIV-positive person who has no symptoms has a CD4 count less than 200. CDC (Center for Disease Control and Prevention in the US) considers HIV-infected persons to have AIDS if they have CD4 counts below 200 (regardless of whether they are sick or well), or a CD4 percentage of less than 14 per cent or an AIDS-indicator illness.