A new portable, low-cost rapid magnetofluidic platform delivers a polymerase chain reaction (PCR) test for gonorrhea and simultaneously detects ciprofloxacin resistance, researchers say. The platform, called PROMPT, could provide faster and more affordable testing for sexually transmitted infection (STI) in low-resource regions and help combat the spread of drug-resistant strains, suggest Dr. Tza-Huei Wang of Johns Hopkins University in Baltimore and colleagues. "Patient follow-up has been notoriously poor for STIs, especially in resource-limited settings - e.g., poor or minority (communities) in high-resource countries," Dr. Wang told Reuters Health by email. "Timely diagnostics to initiate immediate treatment is the key to improved clinical outcomes." "While the latest point-of-care diagnostics research trends towards isothermal techniques," he noted, "our work demonstrates that PCR-based assays can still provide a fast PCR while maintaining high sensitivity and specificity in a cost-effective point-of-care (POC) format." As reported in Science Translational Medicine, Dr. Wang and colleagues developed the PROMPT (portable, rapid, on-cartridge magnetofluidic purification and testing) PCR-test platform because the gold standard methods for STI identification are nucleic acid amplification tests, which are too expensive for widespread use and have lengthy turnaround times. By contrast, PROMPT can detect Neisseria gonorrhoeae with simultaneous genotyping of the pathogen for resistance to the antimicrobial drug ciprofloxacin in less than 15 minutes. The duplex test was integrated into a low-cost thermoplastic cartridge that automatically processed penile-swab samples using magnetic beads. A compact instrument conducted DNA extraction, PCR, and an analysis of results while relaying data to the user via a smartphone app. When applied to 66 penile-swab samples from Baltimore and 151 swab samples from Kampala, Uganda, PROMPT detected infections with a sensitivity of 97.7% and a specificity of 97.6%, and with 100% concordance with culture results for ciprofloxacin resistance. Limitations that need to be addressed before PROMPT can be incorporated into clinical settings, the authors note in the paper, include testing with vaginal and extragenital swabs, and validation of urine samples. Further, they state, "Future cartridges would benefit from higher multiplexing to include assay controls, other antimicrobial resistance markers, or additional STIs such as chlamydia." Dr. Wang said, "The delivery of our devices to clinics will require regulatory approval and collaboration with industrial partners for manufacturing and distribution. We are working toward this goal through forming a university-spinoff and expect to deliver the products within two to three years." "Although ciprofloxacin is no longer recommended for the treatment of gonorrhea in the U.S., up to 80% of gonorrhea infections are still ciprofloxacin-susceptible," he added. "POC use of our platform to rapidly identify susceptible infections opens opportunities for providing access to less expensive oral ciprofloxacin treatments compared to the current first-line recommended dual therapy of injectable ceftriaxone and oral azithromycin." In addition, he noted, "Our platform is based on the commonly used PCR assay, so it can be applied to detect different STIs by using a different test cartridge embedded with PCR primers for the STIs of interest." Dr. Alan Wells, medical director of UPMC Clinical Laboratories and professor of pathology at the University of Pittsburgh School of Medicine, commented on the paper in an email to Reuters Health. "This looks like an interesting development for rapid diagnostics of gonorrhea that could help in many settings where patients are lost to follow-up," he said. "This will provide rapid testing for treatment decisions at that same visit." "The cost issue is still open, as the cartridge manufacturing costs are just a fraction of the actual costs of testing," he added. "Distribution, storage and logistics will add to this cost. Thus, the utility of this test in situations of limited monetary resources, such as the rural clinics in Uganda referred to in the article, is very much in question." "One further issue is that STIs often occur in clusters," Dr. Wells noted. "For this reason, much of the STI testing in the developed world looks for multiple STI pathogens at the same time. The singular testing for gonorrhea leaves open the issues of chlamydia, syphilis and HIV as unanswered, and will require companion diagnostics for these STDs." —Marilynn Larkin Source
