Ellume has developed a digital test system for the rapid detection of both infectious and non-infectious disease, including Group A Streptococcus. The system is designed for use at the point-of-care i.e. physician’s office or pharmacy. The system has three distinct elements including a hand-held graphical user interface, reagents for sample extraction and neutralisation, and a disposable cassette that performs all of the diagnostics i.e. immunoassay, data acquisition and computation.
The core of the technology within the cassette is an inexpensive but highly sensitive fixed point fluorometer that is coupled with exceptionally bright and highly functionalised multi-quantum dot fluorescent microparticles. We use an immunochromatographic test strip as the solid phase, with the fluorescent particles immobilised onto a polyester release pad that is connected to a porous nitrocellulose membrane with a test zone that is coated with specific antibodies and a reference zone. Using a nitrous acid extraction we have been able to detect less than 500 CFU of S. pyogenes in 7 min, which is best-in-class for rapid antigen-based detection. We have shown reactivity to a range of M types of S. pyogenes and no cross-reactivity to other Streptococcus species examined. In retrospective testing against 156 culture-confirmed throat specimens we demonstrated clinical sensitivity of 100% (64/64) and a specificity of 97.8% (90/92).
A large prospective clinical trial of the device is currently underway in 6 clinical sites across Australia. We expect to have performance data relative to both culture and an FDA-approved PCR by late 2017.