Point-of-Care Tests for Sexually Transmitted Infections in Mississippi

As a future physician in Mississippi (MS), it is vital that I continually learn and improve both my thinking and my use of new tools to alleviate health issues in the communities I will soon serve. The problem of sexually transmitted infections (STIs) is one area of healthcare that has a devastating impact on the state of MS, with the Centers for Disease Control and Prevention’s (CDC) 2020 STD Surveillance Report reporting that MS has the highest rates of chlamydia (803.7 per 100k), gonorrhea (462.8 per 100k), and syphilis (24.9 per 100k).¹ Rates of gonorrhea and syphilis have increased yearly in MS from 2016 to 2020, while rates of chlamydia increased yearly from 2016 to 2019.¹ New STIs cost the American healthcare system nearly $16 billion in direct medical costs in 2018, $1.1 billion of which are attributed to chlamydia, gonorrhea, and syphilis infections.² This is why a recent review of point-of-care testing for STIs³ is so compelling and meaningful for current and future physicians worldwide, especially in the state of MS. Because there is such importance in preventing (1) the ongoing transmission of STIs, (2) the often-devastating sequelae of untreated infections, and (3) the recent evolution of antibiotic-resistant gonorrhea, improving our ability to diagnose these infections rapidly and accurately is vital. New and improved POC tests will play a crucial role in accomplishing this goal in the future.

Criteria for developing practical POC tests for STIs, called the ASSURED criteria, have been suggested by the World Health Organization (WHO): affordable, sensitive, specific, user-friendly, rapid and robust, equipment-free, and delivered to end-users.⁴ These criteria are essential for areas with high transmission rates, low rates of return for treatment, insufficient resources, and a high prevalence of asymptomatic infections. While the review article details many different POC tests currently available and in development for T pallidum (syphilis), C trachomatis (chlamydia), N gonorrhoeae (gonorrhea), and T vaginalis (trichomoniasis), I will try to discuss some of the critical points highlighted in the review.

Syphilis is the one STI with POC tests commercially available for diagnosis. Most of the available tests work by detecting antibodies to Treponema pallidum (TP), many with excellent sensitivities and specificities and quick results (5 to 30 minutes). However, one issue with most current tests is their inability to differentiate prior versus present infections. The DPP Syphilis Screen & Confirm Assay by Chembio Diagnostic Systems is currently the only POC test for syphilis that can potentially do this, as it detects both treponemal and nontreponemal antibodies. However, research has shown that, while the DPP test shows excellent sensitivity and specificity for suspected syphilis cases compared to reference serology, the DPP test may miss active infections in patients in early or late latent disease stages who may have lower nontreponemal antibody titers.⁵ This fact is essential to consider when using these tests, especially in populations with a high prevalence of syphilis cases like MS. Additionally, traditional nontreponemal serology tests with numerical values like RPR continue to play an essential role in monitoring treatment effectiveness, something that POC tests like the DPP test cannot currently do.⁶ Despite their flaws, POC syphilis tests like the DPP test might be crucial in detecting disease in populations with a high prevalence, limited diagnostic facilities, and poor follow-up.

POC tests for gonorrhea and chlamydia are often combined, and their number is much lower than for syphilis. Most of them are NAAT-based tests with sound sensitivities and specificities; however, the turnaround times are longer than for syphilis, with one of the best-performing tests, the Xpert CT/NG assay, giving results in 90 minutes. Several trials have assessed this test’s use and have shown that it can reduce transmission and time to treatment. Some of the more exciting developments include the mobiNAAT, which uses a cartridge about the size of a USB drive and works entirely through a mobile phone.

There are several POC tests for trichomoniasis, including the OSOM Trichomonas Rapid Test by Sekisui Diagnostics, which the FDA has cleared. It is an inexpensive antigen test that provides results in 10 minutes with sensitivities ranging from 83% to 90%. Lastly, the paper mentions the development of tests that can detect antimicrobial-resistant (AMR) strains of gonorrhea that are recently becoming more common. While no AMR tests are available, they could help clinical judgment when choosing antibiotic treatment for gonorrhea and other STIs to treat patients more effectively and prevent further evolution of AMR strains.

The development of inexpensive POC tests for STIs and AMR is crucial to stop the increase in STI rates worldwide, especially in places with high rates like Mississippi. Those who create these new tests should use the ASSURED criteria to guide their development. Developing new POC tests for STIs requires significant funding, so partnerships between public organizations and private companies may play an essential role in raising financing, especially in low-resource areas where there is an urgent need for these tests. It may prove necessary for Mississippi’s government officials and healthcare leaders to collaborate and discover how to utilize these new POC tests for STIs to maximize the health of Mississippians, especially those in areas with low resources and physician shortages.