Lateral flow assay (LFA) based diagnostic tests are widely used for point of care (POC) and consumer/self-testing, due to the combination of rapid results with cost-effective testing, achievable by non-specialists. The most well-known application are pregnancy tests. The Clearblue test was the first commercial application of lateral flow technology, in 1988. The unique advantages of LFAs have encouraged the platform to be adopted across a variety of industries, from personal care products to environmental remediation and medical diagnostics. The LFA global market is estimated to be valued $9.65 billion, by 2024.
LFAs are becoming increasingly popular strategies for qualitative, semi-quantitative or quantitative analysis of a variety of target analytes, such as pathogens or biomarkers. An LFA test strip is very simple; involving the chromatographic separation of a test solution across a nitrocellulose membrane and the identification of a specific analyte by binding to antibodies or other affinity reagents on the test strip to give a signal.
POC, or Near Patient Testing (NPT), offers a critical solution in cases of pandemics, for effective mass-monitoring and disease management by enabling rapid detection of the virus away from other susceptible individuals, unlike many diagnostic tests that depend on access to specialised laboratory equipment often found in an hospital environment. Whilst POC testing requires use by a healthcare professional it can still be carried out at bedside, making more laboratory testing facilities available. Consumer, or self-test, devices can be used outside of a healthcare setting and without medical support. Both of these types of test are of particular importance to vulnerable and low-resource communities that do not have access to sufficient laboratory testing facilities. Organisations such as FIND (Foundation for Innovative New Diagnostics) are working in this field to drive innovation in the development and delivery of diagnostics to combat major diseases affecting the world’s poorest populations.
Before a POC test can be recommended by a government, the device must be validated in the appropriate populations and settings. This prevents inadequate testing that would impede disease control efforts, and can therefore have a longer development process than standard laboratory diagnostic tests, with only a subset of tests meeting the necessary levels of accuracy. It is therefore necessary to advance effective disease management through the application of both POC and laboratory diagnostic tests. Through this combinatory approach, using POC for population screening in parallel to highly accurate lab-based diagnostics, healthcare systems will be supported and the need for mass lab-based testing vastly reduced. The WHO has issued specific advice around the current status of POC testing for COVID-19.
The engineered characteristics of Affimer reagents offer benefits in LFA technology, addressing a number of drawbacks commonly seen when using antibodies in this platform for diagnostics. This includes issues of bottlenecks in assay development and production, cost to manufacture, signal sensitivity and specificity, difficult assay targets and assay shelf-life and storage (read more: ‘Improving lateral flow diagnostics with Affimer proteins’). As part of the UK government’s strategy for the COVID-19 outbreak, it aims to scale-up all diagnostic development programmes, to provide testing for anyone that needs it. To achieve this, a triple-pronged approach of more POC and consumer testing, combined with more lab-based testing is required. Avacta has quickly responded to the COVID-19 outbreak, generating multiple Affimer reagents that bind the SARS-COV-2 viral antigen within only four weeks, and working with multiple partners to address all three of these diagnostic markets.
Through our collaboration with Cytiva, our SARS-COV-2 binders will be implemented into LFA test strips to develop both professional POC-use and consumer self-tests. In addition, we are also working with Adeptrix to develop and manufacture an Affimer-based bead-assisted mass spectrometry (BAMS™) COVID-19 antigen test, to support the very high global demand for diagnostic tests. To be used in adjunct to current PCR laboratory testing methods, this BAMS test offers significant expansion of testing capacity, enabling hundreds of samples per day to be analysed by a single technician, whilst using laboratory equipment that is already present in many hospitals but not currently used for COVID-19 testing.
On May 11th, we shipped the SARS-COV-2 Affimer reagents to both Cytiva and Adeptrix to progress development of the tests, read more here.