Rapid Diagnostic Tests Evaluated for HIV/Syphilis

Sexually transmitted infections, such as human immunodeficiency virus (HIV) and syphilis, are among the major health care problems worldwide, especially in low- and middle-income countries. HIV screening programs have been widely used for many years.

The introduction of rapid point-of-care tests (RDTs) that can detect both HIV and syphilis, using one single blood specimen, would be a promising tool to integrate the detection of syphilis into HIV programs and so improve the accessibility of syphilis testing and treatment.

Scientists at the Institute of Tropical Medicine (Antwerp, Belgium) and their international colleagues evaluated the laboratory performance of four dual HIV-Syphilis RDTs. All four assays were evaluated using the same characterized evaluation panel of 400 serum/plasma specimens from European, African, Asian, South American and Australian origin. The panel consisted of 200 anti-HIV antibody positive specimens, of which 100 were anti-TP (Treponema pallidum) antibody positive and 100 were anti-TP antibody negative, and 200 anti-HIV antibody negative specimens, of which 100 were anti-TP antibody positive and 100 anti-TP antibody negative.

The following dual HIV-Syphilis RDTs were evaluated simultaneously: SD Bioline HIV/Syphilis Duo; DPP HIV-Syphilis Assay; Multiplo Rapid TP/HIV Antibody Test. The evaluation of the Insti Multiplex HIV-1/HIV-2/Syphilis Antibody Test, was performed at a later time point. The SD Bioline and the DPP assay are lateral flow (immunochromatographic) RDTs while Multiplo and INSTI are RDTs based on the flow through (immunofiltration) principle.

The investigators reported that in total 400 specimens were tested with each assay, resulting in excellent sensitivities and specificities for HIV, ranging from 99.5% to 100% and from 93.5% to 99.5%, respectively. Results obtained for the Treponema pallidum antibodies were lower, with the lowest sensitivity of 73.5% for Multiplo and the highest of 87% for SD Bioline. Specificities ranged from 99% to 100%. After initial testing, 83.8% (335/400) of the results were in concordance with the Treponema pallidum antibodies reference results in all assays.

The authors concluded that the results of this laboratory evaluation suggest that combined HIV/Syphilis rapid diagnostic tests are a useful tool for the detection of both infections using the same device, and can increase the accessibility of HIV/Syphilis diagnosis for difficult to reach populations in the world. The tests under investigation could further improve in accuracy, especially in the detection of treponemal antibodies, but are promising enough to be introduced into screening programs. The study was published on January 3, 2019, in the journal BMC Infectious Diseases.

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