BRISBANE, AUSTRALIA - A molecular-based, point-of-care test for chlamydia and gonorrhea has shown similar accuracy to laboratory-based testing in a primary care setting, according to new data.
The GeneXpert Chlamydia trachomatis and Neisseria gonorrhea assay was tested in 1,995 individuals participating in the Test, Treat and Go (TTANGO) randomized, cross-over trial in regional and remote Australian primary health care services.
Researchers showed that the assay – which delivers results in 90 minutes – achieved 99.4% concordance with conventional laboratory nucleic acid amplification testing for chlamydia, and 99.9% concordance for gonorrhea.
Courtesy CDC
The GeneXpert system is largely found in hospital laboratories or specialist clinical settings to test for tuberculosis, and this is the first time it has been applied to test for sexually transmitted infections and has been used in a primary care setting, according to Dr. Louise Causer of the Kirby Institute at the University of New South Wales, Sydney.
The results represent a significant improvement on existing lateral flow tests for chlamydia and gonorrhea, which have a high error rate, Dr. Causer said at the World STI & HIV Congress 2015.
“Particularly with chlamydia and gonorrhea, the new technology has allowed for these highly accurate results, whereas before people didn’t use the [lateral flow] tests, even though they were simple and cheap,” she said in an interview.
Of the 14 discordant results, 12 were for chlamydia and 10 of these were a positive point-of-care test, but negative laboratory results. The two discordant gonorrhea results were also both false positives.
Dr. Causer said the discordant results may have been caused by a lower organism load that was close to the limits of test detection.
Centers for Disease Control and Prevention
While staff were trained in using the point-of-care system as part of the trial, Dr. Causer said there were several initial invalid results, which were mostly attributable to the staff getting used to the pipette technique. There was also one incidence of cartridge failure with the device, which resulted in a batch of invalid results.
GeneXpert is already used to test for infections such as tuberculosis, influenza, MRSA, and norovirus, and Dr. Causer said an assay for Trichomonas vaginalis also was being developed.
“It’s the idea that if you invest in the actual platform, you have the potential to adapt it to whatever setting, whatever epidemic is going on,” Dr. Causer said, suggesting there was potential to expand the assay to include other sexually transmitted infections such as HIV and human papillomavirus.
She told attendees at the conference that there is a particular need for rapid point-of-care testing in regional and remote communities, where it can take up to a week for laboratory results to be received, resulting in long delays to treatment and patients being lost to follow-up.
The study received in-kind support from GeneXpert manufacturer Cepheid.