Point of care diagnostics for sexually transmitted infections: perspectives and advances

Abstract

Accurate and inexpensive point-of-care (POC) tests are urgently needed to control sexually transmitted infection epidemics, so that patients can receive immediate diagnoses and treatment. Current POC assays for Chlamydia trachomatis and Neisseria gonorrhoeae perform inadequately and require better assays. Diagnostics for Trichomonas vaginalis rely on wet preparation, with some notable advances. Serological POC assays for syphilis can impact resource-poor settings, with many assays available, but only one available in the U.S. HIV POC diagnostics demonstrate the best performance, with excellent assays available. There is a rapid assay for HSV lesion detection; but no POC serological assays are available. Despite the inadequacy of POC assays for treatable bacterial infections, application of technological advances offers the promise of advancing POC diagnostics for all sexually transmitted infections.

Keywords::

• Chlamydia trachomatis
• HIV
• HSV-2
• Neisseria gonorrhoeae
• PCR
• point-of-care diagnostics
• resource-limited settings
• serology
• syphilis
• Trichomonas vaginalis

Financial & competing interests disclosure

This study was funded by NIH U-54 EB 007958 and NIAID NIH U-01 AM AI 068613. C Gaydos has received research funding and speaker fees from the following: Abbott Molecular, Becton Dickinson, Cepheid and Hologic Gen-Probe. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Although current point-of-care (POC) tests for Chlamydia trachomatis and Neisseria gonorrhoeae have demonstrated less than ideal performance, there are near-patient assays (GenXpert) that have displayed excellent performance characteristics, and new microfluidic-based technologies that offer the promise of excellent POC tests for Chlamydia trachomatis and Neisseria gonorrhoeae in the near future.

• Traditional POC tests for Trichomonas vaginalis still rely largely on wet preparation for detection, although advances have been made with POC tests, notably the OSOM test. The Kalon Tv latex test is another promising technology, although it is not US FDA approved or CE marked, and requires further evaluation before implementation.

• The reverse testing algorithm for syphilis has provided a strategy to identify increased cases of new and previous syphilis infections, although with variable sensitivity. POC tests for syphilis are best utilized in resource-poor settings, although they may have some utility in developed countries among men who have sex with men, or where incidence and prevalence are high.

• There is a FDA-cleared rapid test (IsoAMP) for detection of herpes simplex viruses (HSVs) from lesions, but POC serological assays to measure antibody are not available. Utilizing enzyme immunoassay serological testing to detect HSV antibody is effective in developed countries, although willingness to pay, as well as acceptance by sexually transmitted infection practitioners, are factors affecting acceptability. In developing countries, sensitivity and specificity remain variable, although alterations in testing algorithms and manufacturer cut-offs may improve sensitivity, specificity and consistency in results. For the detection of primary HSV infections, there are some promising new technologies in development (e.g., luciferase immunoprecipitation system).

• Technological advances have led to numerous POC tests for the detection of anti-HIV antibodies, the majority of which show excellent performance in serial or multi-test algorithms. Many are available only outside the USA. The possibility of performing home HIV testing has been advanced with FDA approval for the OraQuick home testing kit, although cost-effectiveness and self-monitoring studies are required to understand the impact home testing will make on overcoming barriers to HIV testing. Numerous technological advances offer the promise of incorporating CD4 as well as p24 antigen testing into POC diagnostics.