When to change treatment

If viral load has not fallen below 50 copies/ml within 12 to 24 weeks of starting a regimen, it may be necessary to switch to different drugs or try treatment 'intensification' – adding additional drugs to further suppress the virus. These strategies are most likely to work when adding drugs from a novel class, since a person’s virus is less likely to be resistant to drugs that work by a different mechanism .

The British HIV Association (BHIVA) advises that viral load should be monitored frequently for a month or so after starting treatment, and again at 12 weeks. If the 12-week viral load test result is in the 50 to 400 copies/ml range, a patient may face a dilemma. Some doctors suggest that people in this situation should wait a few more weeks to allow more time for viral load to fall below 50 copies/ml without using up any more of the available drugs. However, waiting poses the risk that resistance may start to develop, which could also limit future treatment options.

If viral load stabilises above 50 copies/ml – or if it increases – a strong case can be made for adding at least one additional drug or making other changes to the regimen. However, changing therapy based on the results of a single viral load test runs the risk of using up drugs unnecessarily. It is not unusual for viral load to temporarily increase from undetectable to a few hundred or thousand copies/ml, but then return below 50 copies/ml without any change in treatment. These transient increases are called viral load ‘blips’. For this reason, most experts do not recommend changing therapy unless repeated tests indicate that the rise in viral load is real and persistent.

For further information on changing antiretroviral therapy, including treatment intensification, see Changing HIV treatment.