How does secure electronic authentication reduce the risk of point-of-care detection?

For many years, diagnostic testing on human samples was performed exclusively in clinical laboratories. This situation is beginning to change with the emergence of PoC testing, which allows sample processing to be moved to doctors' offices, clinics, hospitals, and even homes. PoC testing has the distinct advantage of eliminating the need to transport patient samples to a centralized laboratory, thereby reducing diagnostic time. It can also significantly improve workflow and provide greater convenience for patients. In the early months of the COVID-19 pandemic, the need for PoC testing became increasingly apparent as delays in testing had a significant impact on society and the spread of the virus.

The trend toward PoC testing will continue, with diagnostic product manufacturers continuing to expand their testing portfolios to include multiple targets, such as respiratory testing kits, sexually transmitted infection (STI) testing, bloodstream infection testing, etc. As this market expands, the number of patient samples processed outside of a laboratory setting is steadily increasing. Today, patient samples are processed not only by professionals in tightly controlled workflows, but also by physicians in clinics and by patients themselves at home, thereby increasing the risk of sample misuse and reuse.

To fully realize the benefits of PoC testing, the system must produce results that both patients and physicians can trust. Test accuracy is key because if the results are inaccurate, misdiagnosis can occur. Even the most accurate tests can cause misdiagnosis if patient samples are not processed correctly. Therefore, taking an approach to ensure correct patient sample processing is critical to generating confident results and reducing the risk of misdiagnosis.

The potential for reuse of patient samples is a major risk factor. This occurs when a swab or test cartridge is accidentally processed multiple times in a testing facility. Picture this: a large family huddled in the kitchen, needing an at-home test before heading out in the morning. It often happens that a parent may accidentally reuse a swab from one child for another. Such risks also exist in clinics or, increasingly, in CLIA-waived laboratories, where trained laboratory technicians are not required to perform diagnostic tests.

A second key risk factor is the potential for intentional misuse of patient samples. For some tests, such as identifying the use of illegal drugs, there may be an incentive for patients to falsify the results. One way to achieve this is to swap sample cartridges before processing. Another challenge in getting accurate results is the presence of counterfeit test kits on the market. In a traditional laboratory environment, procurement occurs through formal channels. For home-based PoC testing, patients typically purchase the test directly from major online retailers. This creates opportunities for counterfeit suppliers, who may have low-quality products that result in less accurate results.

Laboratory environments are not immune to misuse. After use, used sample testing kits in the laboratory are discarded as medical waste. When such medical waste is collected by third parties, there is a risk that sample testing kits will be refurbished and resold to testing laboratories. Labs know nothing about this, and refurbished test kits may look new but either have no reagents or are simply filled with water. This can lead to erroneous test results, leading to inappropriate patient treatment.

Both patients and testing device manufacturers are affected by the reuse and intentional misuse of patient samples. Patients may experience misdiagnosis, such as false-positive tests that lead to unnecessary disruption and unnecessary treatment. Conversely, false negatives can lead to misdiagnosis and ultimately the delay or lack of correct treatment. Inspection equipment manufacturers also pay a heavy price, such as damage to their brand reputation, equipment being labeled inaccurately, or in the worst-case scenario, product recalls. The prevalence of counterfeit and substandard test kits poses significant business risks to testing device manufacturers and has the potential to disrupt the lucrative disposable revenue stream that manufacturers derive from sample test kits.

Two methods have traditionally been used to ensure the authenticity of patient samples. One way is to apply labels, such as 1D and 2D barcodes. The second method exploits mechanical features that prevent the test cartridge from being reinstalled. In laboratory settings, 1D and 2D barcodes are the preferred method for tracking samples. Batch information, serial numbers and unique device identification can be used to ensure the authenticity of the test cartridge. Additionally, barcodes can be viewed before samples are processed to ensure they are not being reused. While barcoding is a reliable way to ensure the authenticity of patient samples, it has limitations. First, barcode labels require a barcode scanner, which can burden instrument design due to size and focal length requirements. Barcodes also require large memory to store a sufficient number of serial numbers to prevent reuse. While this may not be a problem in large lab equipment, for compact PoC devices it will represent cost and size challenges. What's more, because barcodes are visible to users, they are less secure and can be easily copied or counterfeited.

Figure 1. Use of barcodes in PoC systems.

The second traditional method uses simple mechanical features, such as notches on a test cartridge, that change shape or position whenever the test cartridge is inserted into the instrument. Such mechanical features provide a simpler way to prevent reuse and can be implemented in the system at a lower cost. However, because the test kits are identical, it is impossible to differentiate between different patient samples. In addition, because such test boxes are visible to users and often easy to copy, their designs are also easier to counterfeit. Such mechanical properties can also be restored if the test kit is refurbished by an unauthorized party. Due to the small size of PoC devices, adding mechanical features to the detection box creates additional design burden.

Figure 2. Use of mechanical properties in PoC systems.

Finding the ideal solution for the PoC market requires looking beyond these traditional methods and moving towards the form of electronic authentication ICs that can be integrated into test boxes. Electronic authentication ICs reliably prevent the reuse and misuse of test boxes. First, to solve the reuse problem, the electronic authenticator IC integrates a safety down counter to ensure that the disposable detection box is only used once. Integrated unique digital ID distinguishes different patient samples. An integrated challenge-response encryption algorithm mitigates potential misuse and prevents third-party manufacturers from producing counterfeit test kits. Secure authenticator ICs also have additional features, such as the ability to securely record usage history in the form of timestamps. This feature is valuable when testing needs to be done frequently or at specific times of the day.

Figure 3. Electronic authenticator IC in PoC system.

Figure 4. ADI’s secure electronic certification.

Unlike barcodes and mechanical features, electronic authenticator solutions can be integrated inside the detection box, making the security solution invisible to users and potential counterfeiters. Additionally, compact ICs reduce design challenges associated with size limitations of compact PoC instrumentation.

The use of electronic authenticator IC can significantly reduce the risk of sample test kits being reused and misused, thereby ensuring the authenticity and credibility of test results to patients and equipment manufacturers.

Analog Devices' electronic authenticator IC product line provides a turnkey solution that can be easily integrated into a PoC detection box without requiring extensive knowledge of encryption technology.

Each safety authenticator IC has a unique 64-bit serial number for safe identification and traceability of the test box or device. Secure memory protects sensitive data such as manufacturing information and calibration parameters from tampering. The certification uses the industry standard symmetric key SHA-2/SHA-3 or asymmetric key ECDSA encryption algorithm to ensure that the detection box is genuine and prevent the use of third-party counterfeit and shoddy products. An integrated safe down-only counter simplifies usage management and prevents reuse of single-use test cartridges. Key products suitable for PoC applications include the DS28E16, which uses a simple 1-Wire® ^{communication} interface, and the MAX66250, which uses an NFC contactless interface. ADI's electronic authenticator ICs can be integrated into the design without the use of a dedicated PCB, providing a solution that simplifies compact PoC design.

The rise of PoC testing has put forward higher requirements for the safety and traceability of patient samples. Device miniaturization and the high risk factors associated with PoC testing make traditional patient sample tracking methods, such as barcode tracking commonly used in laboratory settings, challenging. Electronic authentication ICs, such as ADI's DS28E16, will simplify the design of PoC instrumentation and help testing equipment manufacturers reduce safety risks, thereby reducing the risk of misdiagnosis, diagnostic delays, or product recalls.