Resistance testing and viral load

HIV can become resistant to antiretroviral drugs. Drug resistance can develop if you are taking HIV treatment that does not fully suppress the virus, and it can cause your current HIV treatment to stop working effectively. Viral load, which should drop when you start a new drug combination, will increase again if drug-resistant HIV develops. This is one of the reasons why taking your treatment as prescribed is so important.

Blood tests can tell whether strains of HIV are resistant to any anti-HIV drugs. In the UK, it is recommended that people have a resistance test before they first start HIV treatment. As a drug-resistant strain of HIV could be passed on, it is important to have this test to make sure that your treatment combination includes drugs that are effective against the strain of HIV you have. You should also have a resistance test if your viral load becomes detectable again, before you change your HIV treatment.

Resistance tests can only be done if your viral load is detectable. The tests most commonly used are thought to work best if your viral load is above 1000 copies/ml.

Now researchers in Canada and Italy have each done studies into how reliable resistance tests are for people with detectable, but low, viral loads.

Both studies found that resistance tests can give reliable results in this situation, even – in some cases – when someone’s viral load was below 200 copies/ml. In addition, doctors could use the test results to predict accurately whether someone’s viral load would continue to increase, suggesting treatment was not working.

The researchers recognised that they are highly experienced in conducting resistance tests and had access to specialised laboratories. However, they believe the outcomes of these studies show that it is possible to use resistance tests at low viral loads, and that doing so will have clinical benefits.

The most important thing you can do to reduce your risk of developing drug resistance is to take your HIV treatment as prescribed (often called ‘adherence’), to give it the best chance of working.

For more information on taking HIV treatment and understanding HIV drug resistance, you may find our Adherence & resistance booklet helpful. It’s available in UK clinics and HIV organisations, and you can view it online at www.aidsmap.com/booklets

Starting treatment and CD4 cell counts

HIV treatment guidelines in the US were changed in 2013, to recommend that everyone with HIV, including adolescents and young adults, start treatment as soon as they are diagnosed, whatever their CD4 cell count. This followed an earlier revision in 2009, recommending people start treatment with a CD4 cell count  of around 500.

Researchers in New York City wanted to find out more about when young people started HIV treatment, and whether there were high levels of transmitted drug resistance (where someone gets a strain of HIV that is already resistant to some anti-HIV drugs).

The study looked at data from the period 2007 to 2011 and found that, in the later period (2010-2011), young people were starting HIV treatment at considerably higher CD4 cell counts than they had been before guidelines changed in 2009. There also seemed to be a significant increase in the amount of transmitted drug resistance, which reduced the options for people starting HIV treatment.

Treatment guidelines in the UK are developed by the British HIV Association. The most recent guidelines for adult treatment were published in November 2013. Currently, these guidelines recommend that, in most cases, people start HIV treatment when their CD4 cell count is around 350, although some people may be encouraged to start treatment when their CD4 cell count is higher – around 500.

Doctors writing these guidelines feel that there is not yet conclusive evidence of benefit of starting HIV treatment earlier for the majority of people with HIV.

Getting and staying in HIV care

With modern HIV treatment, people with HIV can live a long and healthy life. In addition, people who are on effective HIV treatment are much less likely to pass on HIV to others. But for people to start, and stay on, effective HIV treatment, it is important they receive the right services and care at the right time.

For someone living with HIV to achieve an undetectable viral load, they need access to a range of services:

• HIV testing and diagnosis
• appropriate health care and support after diagnosis
• access to HIV treatment if and when they are ready
• support while on treatment.

This sequence is sometimes referred to as the HIV care ‘cascade’. Unfortunately, some people are lost at each step along the way. This can be because of barriers to getting tested, staying in care, and starting or adhering to antiretroviral treatment.

Researchers in British Columbia, Canada, have looked at each step of the care cascade to see whether people accessed, and then stayed in, HIV care after they were diagnosed.

A significant number of people left HIV care at each stage of the cascade. In 2011, only 35% of people with diagnosed HIV had an undetectable viral load – although this was a substantial increase on numbers in previous years.

As in the UK, HIV treatment and care are free to patients in Canada, so cost is not an issue for individuals.

The researchers, and authors of an editorial commenting on the study, call for all governments to monitor people’s entry into, and progress through, the treatment cascade. They feel this would provide useful lessons in how to develop good practice in delivering HIV care, and suggest this work provides a useful model.

It is estimated that only 20% of people with HIV in Europe have an undetectable viral load, despite high rates of HIV diagnosis. However, the UK has a much better record of diagnosis, and of linking people to care and retaining them in care, with just under 50% of people with HIV having an undetectable viral load.  

You can find out more about UK health systems and delivery of care across the world on our website, aidsmap.com.