Novel At-Home Test Diagnoses STIs With ‘Lab-Equivalent’ Accuracy

A novel at-home molecular test proved highly accurate for diagnosing three common sexually transmitted infections (STIs) in females, according to a clinical study from the test’s manufacturer.

The polymerase chain reaction (PCR) test had sensitivity of at least 95% and specificity of at least 98% for chlamydia, gonorrhea, and trichomoniasis, reported Shradha Prabhulkar, PhD, of Visby Medical in San Jose, California, during the IDWeek annual meeting in Los Angeles.

Investigators compared test results from the user-collected vaginal swab samples against those from healthcare provider-collected samples that were evaluated on high complexity assays by trained laboratory professionals. From over 2,200 samples, the at-home test yielded the following results for sensitivity and specificity, respectively:

• Chlamydia trachomatis: 95.2% and 99.0%
• Neisseria gonorrhoeae: 100.0% and 99.3%
• Trichomonas vaginalis: 96.4% and 98.4%

“Chlamydia, gonorrhea, and trichomoniasis are the three most common STIs,” Prabhulkar told attendees. “As you all know, these are easily treatable if diagnosed; but if left untreated, they can lead to severe health consequences, including infertility. What the Visby test can provide are lab-equivalent results for the detection of chlamydia, gonorrhea, and Trichomonas when run by lay users.”

The test kit includes a vaginal swab for self-collection, tube with buffer solution, a PCR test device, and syringe to load the device. The user downloads a phone application that provides video instructions on sample collection and how to run the test. After the user collects a sample and places it in the buffer solution, the sample is then loaded into the PCR test device. The app also takes an image of the results from the device, generates a PDF of the results, and allows the user to connect to telemedicine to access appropriate treatment.

“The user needs less than 2 minutes of hands-on time to test their sample, and the results are a true PCR test result,” Prabhulkar said.

Currently, STI testing and access to treatment can take up to 5 days, including visiting a healthcare provider, waiting for results, and obtaining medication, Prabhulkar pointed out. The at-home test could reduce that process to just 1 to 2 hours, from purchasing the test online or at a pharmacy to having a telemedicine consult, she said.

“This is really impressive,” Dimitri Drekonja, MD, of the Minneapolis VA Health Care System, commented during a question-and-answer portion of the IDWeek session. “I’ve sort of been skeptical of some of the at-home testing; but for sexually transmitted infections, this seems promising.”

“Our labs are typically reporting [STI test results] to state health departments,” he said. “Is there an option where users can do that automatically? Will the device help them, or is it on them to do so?”

Beth Lingenfelter, an executive at Visby Medical, said the company had discussed the matter with the CDC and that the test results report will recommend that clinicians notify the appropriate local health department.

“I think we’re in the right direction, but I don’t think this is ready for prime time yet,” commented Margaret Hammerschlag, MD, of SUNY Downstate Health Sciences University in New York City.

“If you get a positive test, are you going to tell your sexual partner?” she said. She pointed to a survey her institution recently conducted showing that some adolescent girls with STIs failed to inform their partners.

“This is not like doing a rapid strep test or even a rapid COVID test, because of the public health implications,” Hammerschlag emphasized. Her institution’s survey also showed that some adolescent girls had little knowledge of chlamydia and other STIs.

Also, the out-of-pocket cost of such a test could be prohibitive, Hammerschlag noted. Prabhulkar did not disclose a price point for the test.

Daniel Kuritzkes, MD, of Brigham and Women’s Hospital in Boston, questioned if the test manufacturer had plans to sell reagent for the test separately. Otherwise, users would have to repurchase the entire test package and device for subsequent uses, he pointed out. Prabhulkar replied that the device was for single use only, but that the manufacturer was working on device recycling options.

The clinical portion of the study included 2,203 female lay users ages 14 years or older, who performed the test in simulated “at-home” settings across 13 sites in the U.S. Participants had no prior training or help from the study staff.

Investigators also assessed assay performance. No cross reactivity was found for 143 other non-target organisms commonly found in the vaginal microbiome. No microbial interference occurred from 10 genetically similar non-target organisms. The assay was also evaluated for 27 potentially interfering substances and specimen stability. The researchers noted that taking the test on a heavy menstrual flow day “slightly increases the chance the test will not work.”

The at-home test has not been cleared or approved by the FDA.