Viral load is the amount of HIV in your bloodstream. It is measured using one of two techniques; a polymerase chain reaction (PCR test), or a branched DNA (bDNA test).
Viral load tests are an important tool to:
- Monitor HIV progression
While CD4 cell counts are your best measurement of how healthy your immune system is today, viral load tests can help figure out whether you’re at risk for more immune damage in the near future. When compared over time, viral load results tell you whether the amount of HIV in your bloodstream is higher or lower than it was before. The higher your viral load, the more likely you are to lose CD4 cells in the future.
- Figure out when it’s time to start treatment
CD4 cell counts and viral load levels are used together to determine when you may need treatment. You should also consider how you feel, what is going on in your life, and which treatments you will or won’t take or be able to access. The U.S.-based Department of Health and Human Services (DHHS) Guidelines committee makes recommendations on how best to use anti-HIV drugs. The Guidelines state that people with higher viral loads (above 55,000) may be at greater risk for HIV-related complications and should consider starting treatment. Women with HIV may be at risk for developing complications at viral loads slightly lower than 55,000.
- Measure how well HIV drugs are working
HIV drugs work by preventing the virus from reproducing. When a regimen is working, the viral load usually goes down within weeks of starting. If viral load goes up while using HIV drugs, you and your doctor should take another viral load measurement, and look closer to see if there are any problems with adherence or resistance, and determine whether you may need to change drugs in your regimen.
One goal of HIV treatment is to keep viral load levels as low as possible for as long as possible. With effective HIV treatment regimens, viral load can be reduced to levels that cannot be detected by lab tests. With most viral load tests this is below 50 copies per mL of blood.
Even if your viral load is undetectable, HIV is still in your body in very small quantities, in places like the lymph nodes, spleen, and genital tract. If you stop taking your HIV drugs, the virus usually starts multiplying and eventually, the viral load increases.
When Should You Be Tested?
You and your doctor should determine the schedule that works best for you. In general, you should have a viral load test when you are first diagnosed and every three to six months when you are not on HIV therapy.
Consider having a viral load test before starting treatment and another test two to eight weeks later. If the regimen is working to suppress HIV reproduction, your viral load should drop by 90% within two months and be undetectable within six months of starting treatment. Once viral load goes to undetectable, viral load is usually measured every 3 to 6 months.
If these levels are not achieved after starting treatment, or if your viral load has recently become detectable on stable therapy and keeps increasing, it can signal that your regimen isn’t controlling HIV as well as it should. You and your doctor should consider all possible reasons (problems with drug absorption, adherence, or drug resistance) and take steps to correct the problem, including additional testing and considering changing drug treatments.