Field Test Allows Rapid Diagnosis of Chikungunya Virus Infection

RPA-based detection of small amounts of DNA is an alternative to polymerase chain reaction (PCR) and based on reactions that can run at constant temperatures.

An international team of scientists led by those at the Robert-Koch-Institute (Berlin, Germany) included in their study 78 patients with a history of sudden onset of fever, headache, fatigue, nausea, vomiting, rash, myalgia and severe and very painful polyarthralgia suggestive of CHIK infection. Fifty-eight plasma samples were provided by a group in Thailand and 20 CHIKV positive sera samples collected from patients suspected to be infected by CHIKV during routine medical examination, were provided by French scientists.

The team designed a set of CHIKV-specific reagents and showed that the assay was able to detect very small amounts of CHIKV ribonucleic acid (RNA). The RT-RPA assay was slightly less sensitive than RT-PCR, but both assays yielded identical results on clinical samples of 20 patients with known CHIKV infection and 58 samples from suspected cases.

Testing the RT-RPA assay on different CHIKV strains and a panel of related alpha - and arboviruses, the scientists found, that the assay reliably detected all 18 different CHIKV strains tested. In addition, there was no cross-reactivity of the assay with any of the other tested viruses except for the very closely related O'nyong'nyong virus (ONNV). Using a modified set of assay reagents, the scientists were able to eliminate the problem of false-positive results caused by ONNV. The diagnostic sensitivity and specificity of the CHIKV RT-RPA assay were determined at 100%.

The investigators highlighted that RPA reagents are stable at ambient temperature (25-38 °C), meaning they do not need to be refrigerated. The authors concluded that the CHIKV RPA assay is a promising tool for CHIKV diagnostics at the point of need. Integration into a multimer or multiplex assay for simultaneous and detection of CHIKV, Dengue virus and Zika virus as well as an internal control would improve outbreak investigations, since the three viruses induce same clinical picture upon infection and increasingly co-circulate in many parts of world. The study was published on September 29, 2016, in the journal Public Library of Science Neglected Tropical Diseases.

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