Viral load monitoring for HIV

Viral load monitoring for HIV is the regular measurement of the

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.^[2] Variation in cost and the time it takes to get a result may be factors in selecting the type of test used.^[3]

Uses

Viral load monitoring is used by

A count of the viral load is routine before the start of HIV treatment.[1] If the treatment is not changed, then viral load is monitored with testing every 3–4 months to confirm a stable low viral load.^[1] 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.^[1] If a viral load count is not stable or sufficiently low, then that might be a reason to modify the HIV treatment.^[1] If HIV treatment is changed, then the viral load should be tested 2–8 weeks later.^[1]

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

• 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.^[4]

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.

Safe sex practices are recommended for people with low viral load, just the same as for everyone else.^[12] 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.^[12] As of 2010, further research might clarify the uncertainty around that idea.^[12]

History

In January 2008, researchers from Switzerland published what would be termed the Swiss Statement, controversially arguing that HIV-positive individuals 1) on antiretroviral therapy, 2) with a viral load under 40 copies per mL, and 3) with no other sexually transmitted diseases themselves or in their partners could be assumed to not transmit the disease to healthy, HIV-negative partners.^[13] Concerns were raised that blood-based measures of HIV viral concentrations at the time might not reflect actual viral counts in semen, and thus the Statement could encourage needlessly risky sexual practices, though the Statement authors argued they had taken this into account.^[14]

On June 15, 2010, the FDA approved the first diagnostic test capable of detecting HIV antigens and HIV antibodies. The Abbott

The higher the viral load value, the more viral elements there are in blood and other body fluids. For example, individuals with HIV are most contagious during the earliest (acute) stages of the infection, sometimes with millions of copies of HIV per centiliter of blood. According to one estimate, the majority of transmissions among gay men in the UK occur during primary infection.[16] This is because, at this phase, the immune response is still developing. Antibody levels against the virus during acute infection are often too low to be detected, meaning that an antibody test for a highly infectious individual can come back negative.^{[citation needed]}

There is at least one documented case of an HIV-positive individual with an undetectable viral load infecting his partner.^[17] Nevertheless, two recent major studies of serodiscordant couples in which the positive partner had an undetectable viral load have found no linked transmission events despite at least some unprotected sex among the couples.^[18][19] HPTN 052, a third study, found one linked transmission event in a test group of 886 couples,^[20] although it is unclear whether the originally infected partner in this case had achieved an undetectable viral load at the time of transmission.^[21]

Viral load in blood corresponds imperfectly to viral load in other parts of the body. Individuals with undetectable viral loads in their blood might not have undetectable viral loads in other bodily fluids, such as semen or vaginal secretions. In one recent study, of 83 men with undetectable viral loads, 21 had very slight but not undetectable viral loads in their semen.^[22] However, it is unclear how much this actually increases transmission risk.^{[citation needed]}

Distributors

Nucleic acid test

Nucleic acid tests are a typical way to measure viral load, including for HIV.

Non-nucleic acid-based tests

ExaVir™ Load Archived 2011-10-28 at the Wayback Machine Version 3 from Cavidi AB is a largely manual test, which has the European regulatory approval (CE-Mark) for clinical use and is also used for viral load monitoring. Virus-associated reverse transcriptase (RT) activity is measured and can therefore detect all types and subtypes of HIV.^[2] The technology does not require sophisticated laboratories.^[34][35]

References