Almost exactly three years ago, we postulated in this blog that isothermal nucleic acid amplification techniques such as LAMP would prove invaluable in the era of point-of-care diagnostics, and might even have advantages over PCR due to reduced power consumption and increased tolerance of crude samples.
Less than a year after our post, the emergence of a new variant of coronavirus, now known worldwide as Covid-19, spurred on the field of point-of-care diagnostics to make more progress in twelve months than the ten years before.
While lab-based PCR tests and rapid lateral flow tests have been clear winners, the slow turnaround of PCR tests and the low sensitivity of lateral flow tests has left a clear gap in the market for highly sensitive and rapid point-of-care diagnostics. Many companies are now working to fill this gap, alongside unprecedented government investment (such as the US RadX programme) .
While PCR and antibody testing still dominates the market, a plethora of isothermal tests, particularly using LAMP, have emerged – many receiving CE and FDA Emergency Use Approval. Among these are several examples of rapid point-of-care devices that go some way to narrowing the gap between the laboratory and the at-home test.
As we will see, many of the advantages of isothermal testing – simple instrumentation and sample preparation, robustness to inhibitors, and alternative colorimetric detection – have enabled rapid test development and rollout. The immediate need for covid detection also meant that there was no need to address the challenges of multiplexing isothermal techniques.
In Hong Kong, Prenetics has launched the Circle HealthPod – a simple hand-held system comprising a swab, a pre-packaged cartridge and a simple device that interfaces with the cartridge to perform heating, fluidic and optical functions . The simple digital readout completely removes the need for an expert user and facilitates the movement of diagnostics to a home environment. Lucira Health has released a device that produces a nearly identical readout and is already available in the US market .
Another similar system developed by Cue Health provides a cartridge and reader that fit into the palm of a hand and can, in their words, be used ‘anytime, anywhere’ . This system differs from the others by the incorporation of a custom nasal swab that clicks directly into the cartridge, making it exceptionally simple to use. This undoubtedly helped the FDA rapidly grant emergency use authorisation for at-home use. Other devices in a similar format for at-home use are available, such as the Detect system (Detect Health) .
Systems slightly removed from at-home use include the Pebble by Biopix-T . This also uses LAMP but claims to provide a full quantitative readout. It does require mains power and is targeted towards remote healthcare sites such as doctors’ offices and clinics. It does not appear to offer on-board sample processing, which would be a limiting factor for at-home use. The Pebble operates through a smartphone interface and is already available both for covid and flu diagnostics.
C4 Diagnostics has approached the problem via the ‘lab-in-a-suitcase’ route that is again more suited to use by a medical professional . Meanwhile, Canary Global’s DigiGene claims a 60-second multiplex molecular test, although it is not clear which amplification method is used or whether the device has reached the market .
Even for laboratories a range of isothermal kits are available as a simple, fast alternative to PCR. Again the majority are LAMP-based, but other technologies are also in play. The Grifols test, for example, makes use of transcription-mediated amplification .
As we predicted, the use of isothermal amplification techniques has become prominent in the point-of-care market, enabling rapid and specific amplification with minimal equipment. If the industry takes full advantage of this trend, isothermal amplification could become a true at-home diagnostic technology and complete the revolution initiated by the Covid-19 pandemic.
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