More people in the UK are starting HIV treatment early, in order to reduce their risk of transmission

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There is evidence of increasing interest in HIV treatment as prevention among people living with HIV in the UK, with the number of people starting treatment at high CD4 cell counts doubling over a five-year period, according to data presented at a Public Health England meeting this week. In 2013, 49% of those starting treatment had a CD4 count of more than 350 cells/mm3, including 27% with more than 500 cells/mm3.

Whereas some international guidelines recommend beginning HIV treatment at a CD4 cell count of 500 cells/mm3 or earlier, the authors of the UK guidelines do not believe that there is clear evidence that this will lead to improved individual health outcomes. In general, the UK guidelines recommend that treatment is begun with a CD4 count of around 350 cells/mm3.

However, treatment at a higher CD4 count is recommended if an individual has a co-morbidity such as hepatitis B, hepatitis C, tuberculosis, HIV-related kidney disease or HIV-related neurocognitive illness. Pregnant women should also take HIV treatment, whatever their CD4 count.


treatment as prevention (TasP)

A public health strategy involving the prompt provision of antiretroviral treatment in people with HIV in order to reduce their risk of transmitting the virus to others through sex.

statistical significance

Statistical tests are used to judge whether the results of a study could be due to chance and would not be confirmed if the study was repeated. If result is probably not due to chance, the results are ‘statistically significant’. 


Confounding exists if the true association between one factor (Factor A) and an outcome is obscured because there is a second factor (Factor B) which is associated with both Factor A and the outcome. Confounding is often a problem in observational studies when the characteristics of people in one group differ from the characteristics of people in another group. When confounding factors are known they can be measured and controlled for (see ‘multivariable analysis’), but some confounding factors are likely to be unknown or unmeasured. This can lead to biased results. Confounding is not usually a problem in randomised controlled trials. 


The presence of one or more additional health conditions at the same time as a primary condition (such as HIV).



Moreover, since 2012, the UK guidelines have also recommended that doctors should discuss the evidence for the effectiveness of antiretroviral treatment as prevention with all patients with HIV. Regardless of CD4 cell count, any individual who wishes to take treatment in order to protect their partners from the risk of HIV infection should be able to do so.

Uptake of early treatment

In 2008, 75% of the 57,752 adults with diagnosed HIV were taking therapy. By 2013, this had increased to 86% of the 77,702 people with diagnosed HIV.

Looking more specifically at those starting therapy, average CD4 cell counts rose over the five-year period.

Whereas 24% of those starting therapy had a CD4 cell count over 350 cells/mm3 in 2008, this had increased to 49% in 2013. Moreover, the proportions with a CD4 cell count over 500 cells/mm3 rose from 8% to 27%.

Some of those starting treatment at a higher CD4 cell count will have done so due to a comorbidity or as part of a clinical trial, but the significant increase is likely to be due to the increasing awareness of the prevention benefits of HIV treatment.

People aged 25-34, white people and men who have sex with men were more likely to take treatment at a higher CD4 cell count than members of other demographic groups. Individuals who had been diagnosed within a few months of their own infection were four times more likely to start treatment early than people who had been diagnosed at a later stage. People receiving treatment at a larger HIV clinic (with more than 1000 patients) were more likely to do so than people treated at a smaller clinic. All of these differences were statistically significant after adjustment for confounding factors.

Looking at outcomes one year after beginning treatment at a high CD4 cell count, 91% were still taking treatment. However, 5% appeared to have dropped out of care or to have left the country (a similar proportion to other groups of HIV-positive patients in the UK) and 2% were still attending care but no longer taking HIV treatment.

One year on, 90% had an undetectable viral load.

But while results were generally good, some groups had a greater risk of poor adherence and not achieving undetectability, especially younger people. Overall, 23% of those aged 15-24 and 13% of those aged 25-34 did not have an undetectable viral load. Somewhat poorer results were also observed in heterosexual men, people living in deprived areas and those starting treatment with a CD4 cell count above 500 cells/mm3 (rather than between 350 and 500 cells/mm3). These differences were statistically significant after adjustment for confounding factors.

The results show that although the UK treatment guidelines do not recommend that all people with a higher CD4 cell count take HIV treatment, many individuals are choosing to do so. Moreover, the epidemiologists point out that the uptake of treatment is already very high and that changing guidelines to a firmer recommendation for early treatment would only have a limited impact on the total number of people receiving antiretroviral therapy.

In 2012, 60,850 people received treatment. If everyone with a CD4 cell count below 500 cells/mm3 accepted treatment, a further 6100 people would be treated. Providing treatment to every single diagnosed person in the country would add another 6550 people, bringing the total to 73,430.

This suggests that neither the financial impact – nor the public health benefit – of treatment guidelines strongly recommending early treatment would be overwhelming. The public health impact of treatment as prevention is most likely to be realised if fewer people have undiagnosed infection.


Brown A et al. Evidence for HIV treatment as prevention in England, Wales and Northern Ireland. HIV/AIDS Reporters' Meeting, Public Health England, March 23 2015.