The main use of CD4 counts is to know when to start HIV treatment

If HIV drugs were perfect – cheap and effective, with no side effects and no resistance – then everyone would use treatment as soon as they were diagnosed. However, they are not perfect.

This means you need to decide when the risk of not using treatment is greater than the generally low risk of using treatment. When the benefits of treatment are greater than the risks of treatment, it makes sense to use treatment.

At what CD4 count should someone start ARV treatment?

• WHO and UK guidelines recommend people who have no symptoms start ARVs before their CD4 count falls below 350.
• US treatment guidelines recommend people who have no symptoms start ARVs before their CD4 count falls below 500. They also recognise that some people could start treatment at CD4 counts higher than 500 although there is limited evidence to know whether this has benefits over waiting until 500.
• All guidelines recommend people who have serious HIV related symptoms or illnesses start ARVs at any CD4 count.

Several large studies have also shown that people who start treatment with a CD4 count of 350 compared to people starting at 500 or above, get a similar benefit from treatment.

In general, the biggest risks come when the CD4 count is below 200. Most people are unlikely to have HIV-related illnesses when their CD4 count is over 200. This risk is even lower when the CD4 count is over 350.

Several years ago both UK and US treatment guidelines recommended starting at lower levels. Many studies have shown that treatment is safe and effective. More recently approved drugs have fewer risks of side effects. Modern combinations also require fewer pills and numbers of daily doses and this makes taking treatment easier.

Remember that any one CD4 count is just a general figure. It doesn’t matter very much whether you start treatment at 280 or 360 – but generally around 350 is better than waiting until it drops much lower.

In practice, many people who start treatment at much lower levels will still do very well.

Many people are only diagnosed with HIV when they have HIV-related illness and CD4 counts that are under 200.

The risks of complications, treatment failure and side effects increases at lower CD4 counts.