is not impossible to provide mobile, point-of-care viral load tests in
resource-poor settings, the 2014
Treatment as Prevention workshop in Vancouver heard last week. By using a
number of techniques including sample pooling, high throughput, and training
lay testers, it should be possible to provide a viral load for not much more than
the cost of a point-of-care CD4 count.
Lynch of Médecins sans Frontières (MSF) told the workshop that an increasing number
of resource-poor countries were including viral load testing within their
guidelines and that in future, if global guidelines moved, as widely predicted,
towards a policy of universal treatment on diagnosis, then viral load testing
would become more important than CD4 count in terms of monitoring treatment
failure and treatment adherence.
it be afforded, though? Traditionally, viral load tests have been both more
expensive and also not capable of being done in the field, as they rely on DNA
amplification, a technique that has hitherto required bulky laboratory-based
equipment and also a source of mains electricity.
told the workshop that several different point-of-care viral
load testing machines, some battery-powered, were due to come onto the market over the next few years that would make it easy to perform viral load tests in the field. These
would contain an entire automated viral-load testing kit within a machine: all that
is needed is a drop of blood. Results are available within minutes.
four machines MSF studied are the Alere Q HIV test, the DRW SAMBA test, the
Wave-80 EOSCAPE-HIV test, and the Lumora “BART” test.
present, to MSF’s knowledge, 22 low- or middle-income countries incorporate
viral load testing for treatment failure in their guidelines (6 saying it
must be done, 16 as an option) and 12 incorporate viral load testing for
routine monitoring (5 as an expectation, 7 as an option). MSF calculates
that 19 out of 22 countries recommending it for treatment failure and 9 out
of 12 recommending it for routine monitoring are actually unable to afford
viral load testing to the level their guidelines would indicate.
point-of-care (POC) testing be cheaper? Not necessarily, Lynch said, and to
start off with, the per-test cost could be more.
reason is that 63% of the cost of a viral load test is the disposable chemical
reagents and other disposables such as filters that form part of any viral load
test. These cannot easily be made cheaper. Other costs, however, could be lower
with point-of-care testing such as the 11.7% proportion that is due to human resources
such as technicians, and the 1.92% that is lab charges. In addition, the 9.6%
that is due to quality control might be lower in a self-contained machine.
was estimated that the manufacturers’ costs per current, laboratory-based viral
load test varied from $1.61 to $6.77 (average $4.36), with the more recent ones
for which royalties had to be paid costing more. The price paid by wholesalers ranged
from $11 to $25 per test and the final price from $18.62 to $36.38.
was a wide range of costs actually paid by African countries, however. Two,
Kenya and Uganda, had knocked the price per test down to $10.50 while
neighbouring Tanzania paid the region’s highest price at $55.
new point-of-care tests were more expensive because they had features such as
having reagents and vessels contained within special units that were more
expensive to make. As a result the manufacturers’ costs ranged from $4.84 per
test to $9.33 (average $7.28 – nearly $3 more than a lab test).
tests became cheaper as they were used more often. The final cost of a point-of-care test
machine would be about $42 per test if the machine was used to 25% of its
capacity and $33 if it was run at 75% capacity.
however, compares with an average cost of $7.33 for a point-of-care CD4 test.
were other ways of reducing costs. One is to pool samples and then only re-test
samples that produce a positive signal – a particularly economical method if
used in patient groups that are on treatment and mainly expected to have an
undetectable viral load. Sensitivity can initially be set at a figure of, say
1000 or 5000 copies/ml, so only people likely to be infectious are picked out
and not isolated ‘blips’. Pooling samples could reduce costs by 28% if the limit
of detectability was set at 1000 copies/ml and by 51% if it was set at 5000
all other economies, this could potentially reduce the minimum per-test cost
for point-of-care tests from $24 to about $12 – still more than a CD4 count, but not
multiply so. Even more costs could be saved if a decision was taken to stop using CD4 counts for monitoring and only take one initial one.
viral load, Lynch said, it is impossible for sites in resource-poor settings to
know how well antiretroviral therapy is working. The good news is that it was
working at least as well as in richer settings. In one area in Kenya, for
instance, 85% of patients on ART and an estimated 40% of the entire
HIV-positive population, including the undiagnosed, had a viral load below 1000
copies/ml (often used as the threshold for infectiousness) while in another in
Malawi 91% on ART and 62% of everyone with HIV aged 15-59 (thus excluding
children) has below 1000 copies/ml. Two sites in KwaZulu Natal, South Africa,
had achieved viral suppression in 94.7% of diagnosed people within six months
of starting ART.
said MSF was campaigning for an ambitious target of 86% viral undetectability
for everyone living with HIV, diagnosed and otherwise, and was recommending that
international agencies adopt something similar for their goals for 2020.