1. WHEN TO HAVE A VIRAL LOAD TEST. The different times you need a viral load test include:
- Right after diagnosis. This gives what’s called a baseline measurement. Future results can be measured against it.
- Every two to eight weeks at the start of treatment or with a change in treatment.
- This helps to evaluate how well medication is working.
- Every three to six months or as your doctor directs if treatment is effective
Do not have the HIV viral load test within four weeks of any infection or immunization. That’s because these things can throw off your test results.
2. HOW HIV VIRAL LOAD IS MEASURED? There are several different methods for measuring your HIV viral load. It is best to stay with the same method each time because different tests can produce slightly different results. New, more sensitive methods are constantly being developed. These are the three common tests currently used to detect HIV viral load:
- PCR (polymerase chain reaction) uses an enzyme to multiply the HIV RNA in the blood sample. (RNA is the part of HIV that knows how to make copies of HIV.) This makes it easier to measure the amount of HIV RNA in the blood sample. A new ultra sensitive PCR test can measure down to 50 copies of HIV RNA.
- B-DNA (branched-chain DNA) creates a light signal whose brightness depends on the amount of viral RNA present.
- NASBA (nucleic acid sequence based amplification) amplifies the viral proteins, making HIV viral load easier to measure.
3. WHAT HIV VIRAL LOAD TEST RESULTS MEAN? The HIV viral load test measures the number of HIV copies in a milliliter of blood.
- If your HIV viral load is high, HIV is reproducing and the disease may progress more quickly. A high HIV viral load is between 5,000 and 10,000 copies. It can be as high as 1 million or more.
- If your HIV viral load is low, HIV may not be actively reproducing and the disease may progress more slowly. A low viral load is between 200 and 500 copies.
- If your HIV viral load can’t be detected, this does not mean you are cured. The level of HIV virus may be so low that the test can’t pick it up. A more sensitive test may be able to detect it. It’s important to also know that the HIV viral load test does not measure HIV in other parts of the body, where HIV may be present. Only about 2% of HIV is in the blood.
Remember: Even if your HIV viral load is undetectable, you can still infect others.
4. HOW THE HIV VIRAL LOAD TEST IS USED? The tests results have been helpful in many ways.
- Medical research. The HIV viral load test confirms that HIV is present even when CD4 counts are high and no symptoms are present. This means that HIV is not inactive (called latent).
- Diagnosis. The HIV viral load test can detect a viral load a few days after HIV infection and may be useful for early diagnosis. This is quicker than the standard HIV antibody test, which can be falsely negative for two to six months after infection.
- Disease management. Public health guidelines recommend starting antiretroviral therapy if HIV viral loads are higher than 30,000 copies per milliliter of blood with the BDNA test or more than 55,000 copies with the PCR test. These guidelines are for people without symptoms. Other factors will also influence this decision, which you need to discuss with your doctor. For example, if you have symptoms, your doctor may suggest you begin treatment earlier. The HIV viral load test also shows how well medications are controlling the virus. If a drug is working well, it lowers the HIV viral load by 90% within weeks. Within six months, it should continue to drop to fewer than 50 copies.
- Prognosis. HIV viral load results can help predict how long you will stay healthy. The lower your number, the better your prognosis. Some studies show that HIV viral load tests are better than other tests, such as the CD4 count, at predicting the course of the disease. The CD4 count indicates how healthy your immune system is.
- Prevention. The higher your HIV viral load, the greater your chance of transmitting HIV to someone else. In this way, the HIV viral load test has been helpful in predicting risk.