A smartphone-integrated isothermal amplification-based point-of-care testing platform for ultrasensitive detection of severe fever with thrombocytopenia syndrome virus.

BACKGROUND: Severe fever with thrombocytopenia syndrome (SFTS), caused by the severe fever with thrombocytopenia syndrome virus (SFTSV), poses a serious public health threat due to its high fatality rate, and delayed diagnosis is strongly associated with disease progression and increased mortality. Conventional laboratory diagnosis still relies largely on quantitative real-time PCR (qPCR), which requires specialized instruments, trained personnel, and centralized testing facilities. These challenges underscore the urgent need for rapid, sensitive, and portable diagnostic methods for SFTSV detection in clinical and on-site settings.

RESULTS: Here, we developed an integrated isothermal amplification-based point-of-care testing (IAPOCT) platform that incorporates a recombinase polymerase amplification (RPA)-based sensing and interpretation strategy with a smartphone-interfaced portable device. This platform demonstrated low-copy analytical detection capability, achieving a limit of detection (LOD) as low as 10 copies/μL. The core amplification and fluorescence readout steps can be completed within 20 min, while the complete serum testing workflow from thermal lysis to result interpretation requires approximately 25 min. Preliminary evaluation in a cohort of 24 clinical serum specimens showed complete qualitative agreement with qPCR, correctly identifying 20 positive and 4 negative samples. Endpoint fluorescence signals were analyzed through the smartphone-based interface, enabling portable and objective qualitative interpretation of clinical samples. The lyophilized reagent format was incorporated to facilitate handling and integration with the portable testing workflow for routine on-site molecular testing in resource-limited settings.

SIGNIFICANCE: This work provides a practical platform for rapid SFTSV detection with portable fluorescence readout, with potential applications in clinical screening and on-site epidemiological surveillance. By integrating RPA-based amplification, lyophilized reagents, smartphone-assisted interpretation, and a portable device, the platform offers a compact analytical strategy for point-of-care molecular testing of infectious diseases.