Clinical Lab News of the Day – POC rapid test for STI detects chlamydia and gonorrhea simultaneously in two minutes – Molecular-Diagnostics

POC rapid STI test detects chlamydia and gonorrhea simultaneously in two minutes

By LabMedica Editorial Team in Spanish
Updated on 07 November 2023

In 2020, the World Health Organization reported that more than half of the estimated 374 million new sexually transmitted infections were chlamydia or gonorrhea. These diseases often show no symptoms and can coexist, posing significant health risks. If left untreated, they can cause irreparable damage to a woman’s reproductive system. Gonorrhea, which is becoming increasingly resistant to antibiotics, can be fatal if it spreads to the blood and joints. Despite the high incidence, there are currently no rapid tests for either condition. However, this may soon change with the introduction of a lateral flow biosensor that can detect nucleic acids present in chlamydia or gonorrhea from cervical and vaginal swabs in just two minutes.

Existing point-of-care tests for these infections often do not work as well as they should and are not ideal for routine screening during routine doctor visits. Currently, standard tests rely on molecular techniques to detect bacterial nucleic acids, but they can be expensive and time-consuming. Researchers at Pennsylvania State University (University Park, PA, USA) have announced the development of the first rapid tests for gonorrhea and chlamydia. The tests use lateral flow biosensors similar to home COVID-19 tests to identify chlamydia or gonorrhea nucleic acids in swab samples within minutes.

Image: Lateral flow biosensor detects nucleic acids present in chlamydia or gonorrhea in two minutes (Photo courtesy of 123RF)

Like a COVID test, the sample does not require any pre-processing before it is placed in the liquid which allows the material to flow from the reservoir onto a detection strip. This strip contains specially designed nucleic acid fragments, known as single-stranded oligonucleotides (ssDNA), which have a strong affinity for specific genes found in different strains of Chlamydia and gonorrhea. These ssDNAs change color when they bind to the target nucleic acid, indicating a positive result. This technique was validated through an absorbance-based assay; Each ssDNA probe was attached to a gold nanoparticle that has unique optical properties and changes color when the probe binds to its target. The gold nanoparticle diameter is also increased and combined with other nanoparticle probe/sensor complexes to strengthen the signal and deepen the color change.

In clinical trials conducted with 60 unknown samples, the rapid tests correctly identified chlamydia and gonorrhea in every case, with no false negative results. Specificity was slightly lower, over 97%, meaning there were few false positives. However, these results are as good or better than current molecular tests, such as polymerase chain reaction or nucleic acid amplification tests. The researchers also noted that the test design could be modified by replacing synthetic DNA sequences in ssDNA to identify other pathogens.

“There is an urgent need for the development of a point-of-care diagnostic method based on nucleic acid detection with high sensitivity, specificity, and utility,” said Dipanjan Pan, a Penn State researcher who led the study. “Furthermore, since co-infections occur frequently (up to 50%) and have similar symptoms, simultaneous identification and detection of both pathogens is more efficient and cost-effective. To combat the current epidemic of these STIs, it is important to develop a rapid point-of-care diagnostic test that can simultaneously detect chlamydia and gonorrhea.

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