By Marilynn Larkin - October 6th
NEW YORK (Reuters Health) - A newly developed reverse transcription recombinase polymerase amplification (RT-RPA) assay shows promise as a point-of-care diagnostic for Chikungunya virus (CHIKV), researchers report.
CHIKV is transmitted to humans by Aedes mosquitoes, which also transmit the Dengue and Zika viruses. The virus is "currently transmitted in about 60 countries . . . (and) causes acute flu-like symptoms and in many cases prolonged musculoskeletal and joint pain," write Dr. Matthias Niedrig of the Robert Koch Institute in Berlin, Germany and colleagues.
Usually, the infection is detected using RT-PCR or ELISA, "which are not suitable for point-of-care diagnosis," they note.
As reported in PLOS Neglected Tropical Diseases, online September 29, the team developed and tested a rapid, inexpensive and easily deployable alternative based on RT-RPA technology.
Within 15 minutes, the new diagnostic reliably detected and identified 18 different CHIKV strains from the three known CHIKV genotypes.
Dr. Niedrig told Reuters Health, "The clinical sensitivity and specificity of the CHIKV RT-RPA assay was assessed with plasma samples from 58 suspect Chikungunya Fever cases and compared to two CHIKV-specific real-time RT-PCR tests during a field trial in Bangkok, Thailand."
Both RT-PCR tests detected 36 out of 58 positive samples, he said by email. By comparison, "RT-RPA correctly identified all 36 positive samples and correctly identified the 22 negative samples with 100% sensitivity and specificity."
"Additionally, we tested 20 sera from acute CHIK patients from France," he continued. "All three methods efficiently detected 20 out of 20 CHIKV positive samples."
No cross-reactivity was detected to other alphaviruses and arboviruses, except O'nyong'nyong virus, which could be differentiated by modifying the primer, according to the authors.
Dr. Niedrig observed, "Although the first results look very promising, the evaluation has to be enlarged with a higher number of clinical samples to confirm the robustness and usability" of the assay.
"Since we have evaluated the RT-RPA technology successfully also for the diagnosis of other emerging viruses such Ebola, Yellow Fever, Dengue and Zika, we are sure that the advantage of this technology for quicker and reliable diagnosis will be accepted as a serious alternative . . . to real time PCR," Dr. Niedrig concluded.
Dr. Daniel Caplivski, an infectious diseases specialist at Mount Sinai Hospital in New York City, told Reuters Health, "Chikungunya has become an emerging problem in the United States because we have a lot more travelers since 2013, when there was a major outbreak in the Caribbean that quickly spread to the Americas."
"In New York City, we've seen plenty of patients with Chikungunya, mainly because we have a lot of travelers from the Caribbean, Puerto Rico and the Dominican Republic," he said in an interview. "Therefore, this test should be of interest to infectious diseases specialists and emergency room physicians."
Dr. Caplivski noted that physicians currently use a serologic test to diagnose CHIKV, but results "generally come back five to seven days later, so it would be interesting to have an answer right away."
Dr. Christopher Ohl, an infectious diseases specialist at Wake Forest Baptist Medical Center in Winston-Salem, North Carolina, commented, "With all of the attention now being focused on Zika infection, Chikungunya is not getting much attention even though it was recently responsible for a worldwide outbreak and millions of infections."
"Chikungunya is still endemic in many tropical areas and is difficult to distinguish from Dengue Fever and Zika infection," he told Reuters Health by email. "Thus, an accurate test that can be performed quickly in rural and resource-poor settings is quite welcome. This new RT-RPA test should prove to be useful in the evaluation of outbreaks due to mosquito-borne viruses."
No funding was reported. One coauthor is an employee of GenExpress Gesellschaft fur Proteindesign and has a commercial interest in the molecular RNA standard.
Read full publication here
PLoS Negl Trop Dis 2016.