The innovation is called TAGS – short for Temperature-Activated Generation of Signal – and it has the potential to help the way healthcare providers diagnose and ultimately treat infections that have similar symptoms like COVID-19 and the flu, while at the same time reducing cost and environmental waste. With these types of illness, isolating the cause can be critical to providing appropriate treatment.
In 2016, Igor Kozlov together with his colleagues Alison Tsan, Randy Saiki and Amar Gupta in Roche Diagnostics Research & Development set out to double the number of results that could be derived from a single PCR, or
Initially, Kozlov thought that doubling this so-called multiplexing - simultaneously identifying multiple targets in a single test - could not easily be done: “The brightest minds in the field were working on PCR, and I felt it wasn’t possible to come up with a new way to increase multiplexing without making major modifications to existing laboratory instruments or designing completely new ones.”
Roche scientists brainstormed and rejected many early ideas, before discovering that not only could they double the number of results in a single test, they could triple the number of results.
Typically, a single PCR test measures up to five targets (four types of viruses, for example, and one control) on a high throughput analyser through optical detection, with each target identified by a different fluorescent colour. The TAGS technology allows you to measure not one, but up to three targets in the same colour, visible at three different temperatures, for a total of up to 15 targets.
At the lowest temperature, you can see and record the signals from one target per colour. At the medium temperature, you can see two targets per colour, and you identify the second target by subtracting the previously recorded values for the first target. At the highest temperature, you can see all three targets per colour and identify the third by subtracting the already obtained values for the other two.
Kozlov likens the process to imaging a garage with three doors in a desert climate. In the morning, when it’s 58 degrees Fahrenheit, only one garage door opens and you take a picture of what’s inside. If you see a red car, you have a positive result for the first target. At 80 degrees Fahrenheit, the second door also opens and you take another picture. If you see another red car behind the second door after subtracting the first car, you know you have a positive result for the second target. At 91 degrees Fahrenheit, the third door also opens, and you take another image. If you see a third red car after subtracting the two previous cars, you have a positive result for the third target. At night, as the temperature drops back to 58 degrees, the second and the third doors close. “Essentially, you are imaging three red cars, but you control the image by opening the garage doors at various temperatures,” Kozlov said.
The TAGS technique uses two sets of reversible thermo-activated dyes (in addition to the regularly used dyes), where their colours are not visible at lower temperatures but appear at higher temperatures.
“PCR is a cycling process, where you go from low temperature to high temperature maybe 50 times, and with every cycle, you do a measurement. And every cycle, as you go back to the lower temperature, the dyes go back to their non-colorful state,” Kozlov said. “The reversible activation of the dyes is one of the key prerequisites for this technology to work.”
TAGS uses the standard PCR plate on existing high throughput instruments. You get more information per test, which can mean quicker results for patients and lower costs for healthcare professionals. And with no need for additional reagents and consumable parts, there is less waste for the landfill.
Post-pandemic, accurately and quickly diagnosing respiratory viruses and other illnesses is top of mind for many who have overlapping symptoms. With a growing list of new medicines to treat disease, fast, accurate diagnosis is more valuable than ever.
The successful implementation of TAGS technology required dedicated work, great contributions and collaboration by many colleagues in Roche Diagnostics Research & Development, Clinical Development and Medical Affairs, Business, Legal, Quality and Operations.
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