Mouth swab test for HIV could improve detection rates

A MOUTH swab test for HIV that delivers a result in 20 minutes could improve detection rates in Ireland if adopted by hospitals and other treatment centres, a leading virus expert has said.

The HIV saliva test, which uses a toothbrush to pick up HIV antibody markers from the gum line, has recently been made available in Britain where new HIV infections are the highest in western Europe.

Barts and the London NHS Trust, which have conducted 200 such tests since March, believe more people will get tested if the need to draw blood and the long wait for results (normally a week to 10 days) are removed.

Assistant director of the National Virus Reference Laboratory at University College Dublin Dr Jeff Connell said there was a role for this type of testing in Ireland in “certain clinical settings”.

Dr Connell said: “In centres where there is high proportion of people who might be infected or who may have well-established infections, saliva tests are a quick way of identifying HIV-positive individuals and routing them into treatment and preventing onward transmission.”

He said there may also be a case for using such tests in an antenatal environment on patients who have not been assessed prior to presenting.

Another advantage in not having to draw blood is the increased access screening programmes would have to certain groups such as drug users who may not attend clinics and “where blood pressure about the veins is a problem”.

However, Dr Connell warned that saliva tests were not as reliable as the standard laboratory blood tests and were prone to giving false negatives especially in cases where individuals had recently been exposed to the virus.

Studies in the US, where saliva tests have been in use for some time, indicate the tests pick up only 80 per cent of the infections detected by conventional blood tests.

This is because the HIV virus may be present and replicating in the body for a period of up to a month before sufficient antibodies, which would show up on a saliva test, are produced.

Normally saliva test results would have to be confirmed by laboratory blood tests which check for a combination of HIV antibodies and antigens – the substances that trigger an immune response.

Tests that can detect the virus at an early stage of infection are crucial to controlling transmission.

Several US studies indicate that recent undiagnosed infections could be the source of 10-50 per cent of all new HIV transmissions.

A number of pilot programmes in the US have tested individuals for the presence of HIV RNA – the genetic material that transcribes the virus – which appears about one to two weeks before HIV antibodies develop. But routine RNA testing is unlikely to replace conventional testing as it is expensive and involves complicated laboratory work.

The British health authorities have banned home HIV saliva test kits because they believe the tests should be accompanied by counselling services.

By June of last year, some 4,951 diagnoses of HIV had been reported to the Health Protection Surveillance Centre in Ireland since surveillance began.But experts believe the figure may significantly underestimate the level of HIV infection in the State as the system of notification remains voluntary.