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People with HIV considerably overestimate their chance of infecting someone
Gus Cairns, 2016-02-24 10:10:00
Only a small
proportion of HIV-positive people in a large US treatment study, ACTG A5257, regarded
themselves as non-infectious after up to three years on antiretroviral therapy
(ART), and a third of participants regarded their chance of infecting a partner
as still “high”, even though only 10% of participants actually had a detectable viral load, the Conference on Retroviruses and Opportunistic Infections (CROI 2016) heard yesterday.
The study showed that there was no
correlation between a person’s actual viral load and their belief about how
infectious they were, Dr Raphael Landovitz of the University of California in Los
Angeles told the conference.
ACTG A5257 was a large drug-comparison study in which 1809 participants were randomised to receive either raltegravir, boosted atazanavir or boosted
darunavir, plus tenofovir/emtricitabine. The
96-week results were presented at the CROI 2014 conference. The trial enrolled participants
between 2009 and 2011 and patients were asked about their infectiousness beliefs one, two and three years after starting ART, so this study includes responses up to 2014.
A quarter of the study population was women, the mean age
was 37, and ethnicity was distributed quite evenly, with 34% white, 42%
African-American and 22% Hispanic. The median viral load at baseline was 40,000
copies/ml, with 30% having a viral load over 100,000 copies/ml.
The participants were asked the question “How likely would you be to give someone HIV if
you had unprotected sex with them today?”
They rated how
infectious they thought they were on a visual analogue scale, from “not
infectious at all” (zero) to “highly infectious” (100). They were then divided
into four categories: those who thought they were not infectious, and those who
thought their risk of infecting another person was “low” (score 1-33), “medium”
(34-66) or “high” (67-100).
As the start of the study, 58% thought they were highly infectious,
and 26% placed themselves in the “medium” category. This left 16% who thought –
at this point inaccurately – that their risk of infecting another person was “low”
(10%) or zero (6%).
After a year on ART, a higher proportion – just under
one-third – thought their risk of infecting someone was low. But 38% still thought
their infectiousness was high. The percentage who thought they were not infectious
at all had increased slightly to 10%. (Incidentally, 8.1% of this 10% – just eight
individuals – were actually mistaken in their belief at this point, did have a
detectable viral load, and were, to at
least some extent, infectious.)
This hardly changed at all in the subsequent two years. At
week 96, when 90% of trial participants were in fact virally suppressed, 36%
still thought they were highly infectious and 19% were in the "medium" category.
The proportion who thought their chance of infecting others was low had gone up
just one point to 33%, and the proportion who thought they were not infectious
By week 144, after three years on ART, 34% still thought
they were highly infectious and a majority (52%) thought they were highly or
somewhat infectious. The “low” category had increased by two points to 35% and
the non-infectious by two points to 14%.
In other words, after three years on largely suppressive antiretroviral
therapy, the proportion who thought they were highly infectious had roughly
halved and the proportion who believed they were not infectious had roughly
doubled, but these figures in no way reflected the actual proportions who were infectious,
and had no relationship with people’s actual viral load.
At week 48, young people aged under 30 were somewhat more
likely than average to regard their infectiousness as having fallen. Black
people, people with lower educational attainment, and people who entered the
study with a very low CD4 count were less likely.
Women and Hispanic people were more likely to put themselves in the "not infectious" category at week 48, and users of recreational drugs and
those who at baseline had seen themselves as highly infectious were less likely.
The study team will now analyse the data further to find if
people’s beliefs about their infectiousness had any impact on their sexual risk
behaviour and choices of partner.
Given that people’s beliefs about their infectiousness, although
changing somewhat after starting treatment, had little relationship to whether
they were infectious, Dr Landowitz was asked whether
patients were taking over-cautious messages from healthcare professionals to heart,
or felt, due to HIV stigma, that they still had to profess a belief in their own
Dr Landowitz commented that ACTG A5257 spanned the period
during which, in May 2011, the results were announced from the HPTN 052 study,
which confirmed that people with HIV who were on stable ART were rarely
infectious. This result appears to have had little impact on the ACTG A5257
participants. However the trial finished around the time that the even more
study, which found no transmissions from anyone with an undetectable viral
load, announced its interim findings; Dr Landowitz commented that if this
same sub-study was repeated today, people’s beliefs about their infectiousness might
Asked what message we should give to patients about viral
load and infectiousness, he commented: “Don’t give them a dumbed-down message
and talk in absolutes. In my experience, people want nuanced information about
their risk of infecting others and want to be able to make up their own minds.”