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Burst Diagnostics: Capillary Driven Immunoassay (CaDI) to Transform Point-of-Care Diagnostics

(image courtesy of Burst Diagnostics)

A few months ago, I visited the doctor with a sore throat and promptly received an in-office strep test. For those unfamiliar with the test, it involves a gag-inducing swab of the back of the throat followed by a rapid strep test, typically a lateral flow assay. Fortunately, I received a negative strep test result. However, I tried to imagine some of my young children receiving the throat swab and the kind of resistance they might put up to such a test. 

I also later learned that most children and teens are recommended to receive a subsequent 3-day throat culture test. This is to ensure that the more sensitive culture test picks up the strep diagnosis where the rapid test might fail. Thus, not only is there a very uncomfortable initial test, you still have to wait for up to 3 days to find out final results. Many doctors will preventatively prescribe an antibiotic during the waiting period, thus increasing the potential for unnecessary antibiotic use.

What if instead of a throat swab and/or 3-day wait, you could get 20-30 minute results from a saliva test in the doctor's office? After interviewing scientists Zach Call (Diagnostic Platform Lead) and Josi Beck (Product Manager) from Burst Diagnostics, I was pleased to learn that there might just be such a test coming in the future!

And not only can the rapid strep test be improved, but improvements are in sight for many other assays that are currently being performed by lateral flow assays (LFAs) through the use of Burst's Capillary-Driven Immunoassay (CaDI).

The Birth of CaDI: From Academia to Market

In the wake of the COVID-19 pandemic, Burst Diagnostics emerged from the collaborative efforts of innovative scientists from Colorado State University (CSU), including Charles Henry, Professor of Chemistry and Chemical and Biological Engineering; Brian Geiss, Professor of Microbiology, Immunology, and Pathology; and David Dandy, Professor of Chemical and Biological Engineering. This cross-functional team envisioned a new era of diagnostics that could enhance the specificity and sensitivity of LFAs through innovative technology.

Burst Diagnostics was born out of the need for more efficient diagnostic tools. The company’s cornerstone technology, CaDI, was developed as a one-step enzyme-linked immunosorbent assay (ELISA) that retained the user-friendly nature of an LFA. This innovation came to life in 2020 during research initially focused on COVID-19 diagnostics.

The CaDI technology is a microfluidic assay platform created via deposited reagents on patterned layers of polyester and adhesive. The efficient, yet customizable, nature of the device makes it a platform that has the potential to significantly improve upon traditional diagnostic methods. 

Reagents are embedded with the patterned microfluidic channels, including capture antibodies printed on a nitrocellulose pad. As solution is added to the CaDI, the fluid migrates through the device enabling the multi-step reactions and interactions to take place. In the end, there is a final readout step that enables the detection of the analyte of interest.

The use of low-cost materials and manufacturing processes has helped CaDI make the leap from academic research to a market-ready product in just a few years. The goal is to deliver high-sensitivity diagnostics to clinical, research, and even at-home settings.  In addition to an improved rapid strep test, Burst is also currently working on STI and respiratory infection detection assays.

Image of microfluidic device (image courtesy of Burst Diagnostics)

Improving the Diagnostic

Beyond the microfluidic design elements, Burst Diagnostics has made significant strides with the addition of chemiluminescent detection, which offers superior sensitivity compared to traditional colorimetric tests. By utilizing chemiluminescence and integrating a user-friendly instrument read-out, they have developed assays that are far more sensitive and precise. 

It is this enhanced sensitivity that has the potential to deliver a rapid strep A using a saliva sample rather than a throat swab. The chemiluminescent sensitivity can pick up on the lower concentration of strep A proteins found in saliva and eliminate the need for the throat swab. This higher sensitivity also has the potential to reduce or eliminate the need for the backup culture test.

Additionally, the reader technology, developed in collaboration with Zymo Research, implements machine vision software which eliminates visual guesswork from a colorimetric LFA and provides the kind of accurate reading preferred for decision-making medical diagnostics. 

Image of Burst Diagnostic Reader (image courtesy of Burst Diagnostics)

The CaDI platform's versatility allows for the adaptation of various assay formats, including wellness tests and small molecule detection. The flexibility of CaDI also enables Burst to work with collaborators on developing tailored solutions for specific diagnostic needs. 

Moreover, comparative studies have shown CaDI to be 100 times more sensitive than existing LFAs underscoring its competitive edge. Burst intends their assays to be competitive with PCR assays in sensitivity, while maintaining the ease of use and user-friendly nature of an LFA.

Current Challenges and Next Steps

What does the future hold for Burst Diagnostics? The team faces several common challenges inherent to new technologies at this phase of development. They are working to navigate regulatory hurdles and secure the necessary partnerships and funding for clinical trials and FDA submissions. They are also continually looking to find the right partners to help them move their platform forward in ways that will impact the diagnostic market. 

Looking further ahead, the team also understands the challenge of market adoption for a new diagnostic technology. The scientists at Burst recognize the need to stay in tune with current and future customer needs and modify the technology appropriately. With a focus on the customer, Burst Diagnostics aims to break through entrenched preferences for traditional LFAs and PCR tests by demonstrating the superior performance and convenience of the CaDI technology.

Vision for the Future

Burst Diagnostics envisions a future where diagnostic power is literally in the palm of your hand, accessible whenever and wherever needed. Their mission is to improve the diagnostic field by merging high sensitivity and specificity with user-friendly applications, ultimately aiming to improve patient outcomes and healthcare efficiency. In the meantime, look out for a much improved, much easier-to-use rapid strep test!

For more information about Burst Diagnostics, visit their website at or contact the team at

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