New technology for decentralised and low-cost mass testing
Researchers are developing a highly specific and sensitive method to detect SARS-CoV-2 antibodies in dried blood samples, enabling large-scale testing at home.
Because a large number of people infected with SARS-CoV-2 have no or only mild symptoms, many Covid-19 infections are not detected by PCR and antigen tests. However, testing is important to measure the actual spread of the virus and its variants and to learn how many people have actually been exposed to the virus and how it has spread.
Sebastian Maerkl and his research team at EPF Lausanne have developed a reliable method that allows a large number of people to be tested for specific antibodies to SARS-CoV-2 in blood samples with little effort. This information is important for tracing the course of the pandemic over time.
Dried blood samples are suitable for large-scale measurement of the spread of SARS-CoV-2 due to their ease of handling. Collecting dried blood samples doesn't require trained personnel - anyone can create samples from home with a self-collection kit. A tiny drop of blood is obtained by a prick in the fingertip, which is collected with a container and conveniently sent back to the lab by postal letter.
This sensitive and specific method, called high-throughput nano-immunoassay (NIA), can analyse 1024 samples of dried blood in parallel for antibodies to SARS-CoV-2. A small team of two people has already analysed more than 3,200 blood samples, resulting in more than 24,000 immunoassays.
The new method was successfully applied in practice last year. The research teams of Silvia Stringhini and Isabella Eckerle measured the prevalence of Covid-19 in two- to four-year-old children at the beginning and end of the school year as well as during the various SARS-CoV-2 outbreaks. The method was also used in the Canton of Vaud for the SerocoViD study. This study assessed the share of the population that has developed an immune response to coronavirus through infection.
With their approach, the researchers enable simple and decentralised blood sampling. Such large-scale serological testing can be used in connection with SARS-CoV-2. For this purpose, an appropriate seroprevalence survaillance programme would have to be set up in collaboration with the government and cantons. In addition, the method can be adapted to new virus variants such as Omicron and scaled up in preparation for further pandemics. This also makes it useful for protein biomarkers of other diseases.
Swank Z, Michielin G, et al. A high-throughput microfluidic nanoimmunoassay for detecting anti–SARS-CoV-2 antibodies in serum or ultralow-volume blood samples. PNAS May 4, 2021 118 (18). DOI: https://doi.org/10.1073/pnas.2025289118
Lorthe E, Bellon M, et al. Epidemiological, virological and serological investigation into a SARS-CoV-2 outbreak (Alpha variant) in a primary school in Geneva, Switzerland: a prospective longitudinal study. SEROCoV Schools Study Group. medRxiv 2021 10.26.21265509. DOI: https://doi.org/10.1101/2021.10.26.21265509