Understanding the CD4:CD8 Ratio Test

The CD4:CD8 ratio test measures two types of white blood cells crucial for your immune system. It's mainly used to monitor HIV infections but can also help with other conditions, such as mononucleosis or chronic lymphocytic leukemia. This test provides valuable insights into your immune system's strength and helps doctors tailor treatment plans for various health issues.

CD4 cells coordinate immune responses by signaling other cells to attack invaders. CD8 cells directly attack and kill infected or cancerous cells. In HIV infections, the virus targets CD4 cells, leading to a low CD4 count and an imbalanced ratio of CD4 and CD8 cells. If you have an HIV infection, your CD4:CD8 ratio test results can help your doctor know how active the virus is in your body and how you're responding to your medicine.

A normal CD4 count typically ranges from 500 to 1,200 cells per milliliter of blood. If you have an HIV infection and your CD4 count falls below 200 cells per milliliter of blood, your doctor will likely diagnose you with AIDS. A CD4 count this low significantly increases your risk of developing life-threatening infections and cancer. A normal CD8 count generally ranges from 150 to 1,000 cells per milliliter of blood.

The CD4:CD8 ratio is calculated by dividing the CD4 count by the CD8 count. A normal ratio falls between 1 and 3. A ratio below 1 may suggest an untreated HIV infection, ineffective HIV treatment, or other health issues, such as anemia or multiple sclerosis. Your CD4:CD8 ratio may be higher than 3 if you have a serious bacterial infection, a viral infection (such as COVID-19), or some type of blood cancer.

For HIV patients, the CD4:CD8 ratio test helps track treatment effectiveness and immune system recovery. A CD4 count above 500 cells per milliliter indicates controlled HIV infection. Regular testing every three to six months while on antiretroviral therapy helps doctors monitor progress. It may take years of consistent treatment for CD4 counts to return to normal levels.