Multiplex, Point-of-Care Test for STIs Could Offer Public Health Benefits

Point-of-care (POC) testing that could simultaneously identify multiple sexually transmitted infections (STIs) could be a valuable addition to sexual health clinics, according to a U.K. study published Sept. 10 in BMJ Open. Such a test, if commercially available, would benefit patients, cut transmission of STIs, and reduce unnecessary antibiotic prescribing.

In addition to the personal, long-term reproductive-health consequences for patients, STIs pose a public health concern and antibiotic stewardship headaches. In symptomatic patients, empirical antimicrobial therapy is usually guided by results of immediate microscopy of genital discharge, but this approach is known to have low sensitivity—missing up to half of Neisseria gonorrhoeae (NG) and Trichomonas vaginalis (TV) infections in women—and having poor specificity for predicting Chlamydia trachomatis (CT) or Mycoplasma genitalium (MG).

Currently, routine diagnosis requires laboratory-based nucleic acid amplification tests (NAATs), which can take up to two weeks for return of results. In the United Kingdom most genitourinary medicine services do not routinely conduct NAATs for MG or TV.

However, emerging POC tests enable testing for multiple STIs, which could address antibiotic stewardship challenges and improve patient and public health outcomes. Presumably, POC tests would require fewer clinic visits, reducing the number of patients lost to follow-up and saving patients time, money, and anxiety. Diagnosing at STIs at the initial clinic visit would improve STI management.

The U.K.-based researchers built a model to assess costs, benefits, and cost-effectiveness of three testing strategies using microscopy plus hypothetical NAAT POCTs that deliver results in 30 minutes for a dual chlamydia and gonorrhea test, a triple test that also includes M. genitalium, and a quadruple test which also includes trichomoniasis, compared current practice of using microscopy plus a laboratory NAAT for chlamydia and gonorrhea.

The model used a hypothetical cohort of just under 1 million people with symptoms of a lower genitourinary tract infection attending English genitourinary medicine service. The model considered costs (e.g., staff time, diagnostic kit, drugs and other consumables) and reimbursement to genitourinary services associated with diagnosing and managing STIs, but did not include long-term complications associated with STI infection (e.g., infertility) other than pelvic inflammatory disease. The model also assumed that treatment was started on the day of diagnosis. Sample average costs included $17.22 for a CT-NG NAAT laboratory diagnostic test, $31.37 for a POC CT-NG test, $37.91 for a POC CT-NG-MG test, and $44.44 for a POC CT-NG-MG-TV test.

The researchers found that the current standard of care was the cheapest strategy when considering the costs to genitourinary services, with all three POC strategies adding additional expenses—a 5 percent increase for the dual POC test, a 10.4 percent increase for the triplex POC test, and 10.8 percent increase for the quadruplex POC test. However, when looking at payment by results, the tariff-based reimbursement), the standard of care became the most expensive and the quadruplex POC test became the least expensive.

Specifically, the quadruplex POCT was the most cost-effective relative to the other strategies, using tariff costing, saving an estimated $34.6 million (mostly in averted clinic visits). The quadruplex POC test also generated the most other benefits, including 240,467 fewer clinic visits, 808 fewer STI transmissions, and 235,135 averted inappropriate antibiotic treatments, compared with the standard of care.

“POC pathways generated some cost-savings, primarily because patients had fewer return visits. However, these did not outweigh the higher cost of the POC tests compared with laboratory-based NAATs when estimating total pathway costs,” write the authors led by Susie Huntington, Ph.D., from Aquarius Population Health in the United Kingdom. “Cost implications are driven by the cost of POC tests and would vary somewhat in different geographical areas due to differences in the subgroup mix and the prevalence of the four STIs.”

While there are no triplex or quadruplex POC STI tests currently on the market, there is at least one multiplex STI POC assay in development.

Takeaway: A multiplex, POC test for STI may offer patient-level and public health benefits, despite the potential increase in cost.