Oral HIV tests yield accurate results in southern Africa

Two oral HIV tests have been shown to be highly accurate in a study conducted in Namibia and reported in the May 1^st edition of theJournal of Acquired Immune Deficiency Syndromes. The studies were conducted amongst patients infected with HIV subtype C and the OraQuick test was shown to be 100% accurate with the OrSure test being 98.9% accurate. The investigators believe that oral HIV testing could be used to help diagnose HIV in resource-limited settings, and assist in the gathering of surveillance information.

In order to design appropriate prevention and treatment initiatives it is important to have accurate HIV surveillance information. This is particularly the case in southern Africa where the HIV epidemic continues to expand. Oral fluid tests have the potential to be useful tools in these surveillance projects.

Two oral HIV tests have been approved in the US (OraQuick and OraSure) and have been shown to be able to accurately diagnose HIV infection. But studies into the accuracy of these tests were conducted in countries where the majority of patients are infected with HIV subtype B. There is very little information about the accuracy of these tests in settings where the majority of HIV infections involve non-B subtypes.

Investigators therefore designed a cross-sectional (or “snap-shot”) study to assess the accuracy of these two oral HIV tests. The study population involved 273 pregnant women of unknown HIV status in Namibia. The predominate HIV subtype in this region is subtype C.

Two oral fluid samples were collected using both the OraQuick and OraSure tests. Blood samples were also taken from the women and tested for antibodies to HIV to assess the accuracy of the oral tests.

Blood tests showed that 70 (26%) of the women were infected with HIV. OraQuick results were available for all 273 women and were 100% accurate. Six of the OraSure results were excluded because they were not labelled properly, and three results (1.1%) did not agree with the results from the paired blood test. This included two false-negatives and one false-positive.

The investigators think that the two false-negatives could have been because not enough oral fluid was collected, or because the patients had very low levels of HIV antibodies.

“To our knowledge, this study is the first to report ELISA [blood] test performance with oral fluid in a population predominantly infected with subtype C”, write the investigators. They add, “in view of the dominance of subtype C in high-prevalence areas, such as southern and east Africa and India, validated oral fluid tests can be of great value to enhance surveillance efforts where these are most needed.”