Oral fluid-based HIV testing found reliable
R. PRASAD
IF CREATING awareness and convincing people to go to voluntary counselling and testing centres (VCTC) for HIV testing has been a Herculean task, getting people to come back to get their test results has not been easy either.
The US based Centres for Disease Control and Prevention (CDC) had brought out the importance of a rapid HIV testing. Of the 2.1 million HIV tests conducted every year in the counselling, testing and referral (CTC) programs, nearly 30 per cent who tested positive and about 39 per cent who tested negative for HIV did not turn up to collect their results.
So in March 2004 when the US Food and Drug Administration (FDA) approved, for the first time, OraQuick for rapid testing for HIV using oral fluid specimen, there was a sense of relief.
Immediate results
The results from such a rapid testing, as the name implies, are immediate and thus obviate the need for a second visit to collect them.
And when the testing procedure is non-invasive, the willingness to get tested is greater. Another advantage is that it is suitable for resource-constrained settings, such as rural India.
The sensitivity and specificity of oral fluid-based HIV testing were claimed to be very high till a study in December 2005.
False positives
The study showed that the number of false positives (testing positive even when the person is not infected with HIV) was unusually high.
However, a study published in PloS One journal in January 2007 and done primarily to find out the incidence of false positives when oral fluid-based testing was used found that it had 100 per cent specificity (no false positives).
The study was done in nine cities in the US and all tests were confirmed using the standard Western blot method.
High specificity
A report published recently (April 2007) in the journal PloS One and based on a study done at the Mahatma Gandhi Institute of Medical Sciences (MGIMS) based in Sevagram, Wardha district, also found that the specificity of oral fluid-based testing was 100 per cent.
It also showed similar results for sensitivity. The study was based on the results obtained from 450 participants.
Though it is known that the sensitivity and specificity are high when OraQuick oral fluid-based testing is used, will the cent percent obtained on both the parameters be really reliable?
Primary objective
According to the authors, the primary objective of the study was to study the sensitivity and specificity of the testing procedure.
Hence, all participants were checked for their HIV status using oral fluid and OraQuick's finger stick method and finally using the ELISA/Western blot confirmatory test.
"We found that the oral mucosal fluid test was 100 per cent accurate.
... The OraQuick test yielded no false positive results," the authors noted in the paper.
They also noted that oral testing was: "... rapid, easy, feasible, and convenient even in a rural hospital setting in India.
These characteristics have the potential to encourage people to present for voluntary HIV testing. ... Oral fluid-based rapid HIV testing may work well in rural resource limited settings, and greatly enhance the control of the HIV epidemic in poor countries."
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