SOUTH AFRICA: Rapid HIV tests not
infallible
JOHANNESBURG, 6 October 2008
(PlusNews) - The reliability of HIV
diagnoses obtained from finger prick
tests has come into question with
the recall of a brand of rapid HIV
test kits used at public testing
sites in two South African
provinces.
A local newspaper reported on 28
September that more than half a
million Wondfo Rapid One Step Test
kits, manufactured in China and
supplied by FutureMed
Pharmaceuticals, were withdrawn in
late July after they were found to
be defective.
The development of rapid HIV tests,
which provide results in less than
30 minutes and can be carried out
with minimal equipment or training,
has greatly increased both the
accessibility of testing and the
numbers of people tested.
Miriam Mhazo, a senior programme
manager at New Start, a non-profit
organisation that provides voluntary
HIV counselling and testing (VCT)
services throughout the country,
told IRIN/PlusNews that before her
organisation starting using rapid
tests in 2004, clients had to wait
eight days to receive their results,
and "about 30 percent wouldn't come
back."
But several recent studies have
uncovered problems with the
performance of certain brands of
rapid test kits, and with the level
of user error in busy public health
facilities where they are used.
User error
A study at 12 sites providing
prevention of mother-to-child
(PMTCT) services in KwaZulu-Natal
Province evaluated HIV rapid tests
performed on 961 women.
"There have been isolated reports of
false positive results with rapid
HIV tests in KwaZulu-Natal," said
the study's lead investigator,
Dhayendre Moodley of the Women's
Health and HIV Research Unit at the
University of KwaZulu-Natal.
"Surprisingly, most of these tests
are FDA [US Food and Drug
Administration] approved, as well as
evaluated and approved by our
National Laboratory Services, prior
to their use in the public health
sector. We therefore decided to
determine if the error lies with the
test or with the user."
Four different brands of rapid tests
were evaluated and test results
obtained by nurses and counsellors
were compared to those obtained by
laboratory technicians. Accuracy was
determined according to whether two
tests achieved the same result for
the same individual - "concordance".
The study found that whereas the
laboratory technicians using the
rapid tests achieved 100 percent
concordance, the nurses and
counsellors achieved only between 92
and 98 percent.
Although some brands of test kits
were slightly more sensitive than
others, they all met World Health
Organisation standards when
performed in laboratories.
The investigators concluded that
only user errors, such as applying
an incorrect volume of the
activating agent, could explain why
the tests yielded less reliable
results when performed by nurses and
counsellors. Other problems could
include incorrect interpretation of
results or misidentification of
specimens or tests.
"With any kind of laboratory test,
one needs to follow the
manufacturer's instructions to every
detail," commented Moodley. "With
these tests, the instructions are
very clear and simple, and if people
are trained and follow the method,
there shouldn't be a problem."
In an article published in the
September issue of the South African
Medical Journal (SAMJ), Moodley and
her colleagues recommended more
ongoing training and supervision of
health workers carrying out rapid
HIV tests, and a system to ensure
quality control.
She noted that although guidelines
for regularly comparing rapid test
results with the results obtained
from more sophisticated laboratory
tests were in place, they were not
being implemented at all health
facilities.
Devastating consequences
The consequences of receiving an
incorrect HIV test result are
potentially devastating. Someone who
has received a false negative result
could unknowingly infect others and
also miss the opportunity of
receiving treatment, while false
positive results could sometimes
lead to "severe physical trauma from
partners, abandonment, and
suicides", the SAMJ article said.
(Embedded image moved to file:
pic08838.jpg)''?We need to be more
selective in the types of rapid
tests we use(Embedded image moved
to file: pic14844.jpg)''?
Moodley recalled some isolated cases
where patients had participated in
clinical trials because they had
tested HIV-positive at public health
facilities, only to discover they
were negative when tested by
laboratory tests.
Another recent study, also conducted
in KwaZulu-Natal, tested four
different types of rapid HIV test
kits and found them to be less
reliable than the manufacturers
claimed: of the 751 patients who
tested negative or had discordant
results from rapid tests, 19 turned
out to be HIV-positive.
The authors concluded that rapid HIV
tests could lead to "substantial
numbers of false negative results"
in a high-prevalence setting like
South Africa.
"We welcome the rapid test, knowing
the laboratory constraints the
country faces, and the benefits of
getting results on the spot,"
Moodley said. "But I believe we need
to be more selective in the types of
rapid tests we use, and that
selection should be based on prior
field evaluation, in addition to
laboratory evaluations."
ks/he
Themes: (IRIN) HIV/AIDS (PlusNews)
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