Viral load monitoring for HIV is the regular measurement of the viral load of individual HIV-positive people as part of their personal plan for treatment of HIV/AIDS. A count of the viral load is routine before the start of HIV treatment.
Types Various viral load tests might be used. One way to classify tests is by whether it is a nucleic acid test or non-nucleic acid test. Variation in cost and the time it takes to get a result may be factors in selecting the type of test used.
Uses Viral load monitoring is used by HIV-positive people to develop a plan for their personal treatment of HIV/AIDS. A count of the viral load is routine before the start of HIV treatment. If the treatment is not changed, then viral load is monitored with testing every 3–4 months to confirm a stable low viral load. Patients who are medically stable and who have low viral load for two years may get viral load counts every 6 months instead of 3. If a viral load count is not stable or sufficiently low, then that might be a reason to modify the HIV treatment. If HIV treatment is changed, then the viral load should be tested 2–8 weeks later.
Typical interpretation of results Previous treatment guidelines recommended that anyone with a viral load greater than 100,000 copies/mL of blood should begin treatment. It is now standard of care in the United States to begin anti-retroviral treatment upon discovery of HIV positive status. HIV is a retrovirus, an RNA virus that enters a host cell and uses the host DNA replication machinery and the enzyme reverse transcriptase to produce DNA from the viral RNA genome. HIV also produces an integrase enzyme which is used to integrate the newly produced viral DNA into the host's DNA. The virus is then replicated every time the host cell's DNA replicates. Due to the nature of the virus the drugs used to treat HIV are called antiretroviral medicines, and the course of treatment is called antiretroviral therapy (ART). These potent medicines cannot cure an individual; they can however manage the virus and slow the progression of the HIV infection. Strict compliance with the prescribed ART regimen is vital to controlling the disease. Highly active antiretroviral therapy (HAART) is the current recommended treatment for HIV. HAART entails taking a combination (regimen) of three or more ART medications from at least two different classes of drugs. There are six classes of ART medications:
non-nucleoside reverse transcriptase inhibitors (NNRTIs) Nucleoside reverse transcriptase inhibitors (NRTIs) protease inhibitors (PIs) entry inhibitors Fusion inhibitors Integrase inhibitors Each class of medications uses a different mode of action to blocks the virus. Treatment is more effective in controlling the virus when a combination of medications from different classes is used. HAART also reduces the risk of developing drug resistance. Viral load tests are used to monitor the effects ART, to track viral suppression, and detect treatment failure. Successful combination ART should give a fall in viral load of 1.5 to 2 logs (30-100 fold) within six weeks, with the viral load falling below the limit of detection within four to six months. Laboratory monitoring schedule for patients using ART:
CD4 count indication Viral load monitoring for HIV complements the CD4 count, which is another sort of test associated with monitoring HIV. Confusion about when to take a CD4 test is common. The results of a viral load test help determine when a CD4 count is indicated. CD4 cells are the primary target of HIV. A CD4 test quantifies Helper T cells and is often combined with viral load testing to monitor the progression of HIV. CD4 testing shows the strength of the immune system, but does not report viral activity. As established by the Centers for Disease Control and Prevention (CDC), a person with HIV and a CD4 count below 200 or a CD4 percentage below 14% is considered to have AIDS. An increased CD4 count can result from an immune response to an infection or a recent vaccination. A decreased CD4 count, in combination with higher numbers on a viral load test, indicates an increased risk of getting sick from opportunistic diseases.
Blips in data While receiving ART some patients with undetectable viral load measurements may experience an increase in viral load, to a low level (usually below 400 copies/mL blood), and then returned to an undetectable level. These transient blips do not indicate that the virus is developing resistance to drug therapy. Blips appear to be more common in the winter, suggesting a connection with illness such as colds and influenza. Viral load blips are partially explained by various patient related factors, and thought to be relatively common. High level and sustained increases in viral load are frequently related to the development of drug resistance and/or viral mutations, and often dictate changes in ART.
Special populations The window period for a test is the amount of time from the initial infection event until the disease can be detected. Exposure to HIV, followed by replication of the virus, may take as long as six months to reach a level detectable in many testing methods. An HIV antibody test usually detects the HIV antibodies within two to eight weeks, but can have a valid negative result for a long as 2 to 6 months after initial infection. Viral load tests can also be used to diagnose HIV infection, especially in children under 18 months born to mothers with HIV, where the presence of maternal antibodies prevents the use of antibody-based (ELISA) diagnostic tests. Pooled viral RNA testing shortens the window period to a median of 17 days (95% CI, 13-28 Days). Although it is not the standard of care to use this test for diagnosis, in communities with high HIV prevalence, this test has a significantly improved negative predictive value over 3rd and 4th generation tests for detecting acute HIV infections.
Adverse effects Safe sex practices are recommended for people with low viral load, just the same as for everyone else. Researchers have questioned whether people who are told that they have a low viral load will respond to this information by lowering their use of safe sex practices. As of 2010, further research might clarify the uncertainty around that idea.
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