This last week has been a rollercoaster ride for many of us with ambitions of scaling testing for SARS-CoV-2. It has been a rollercoaster ride for those who believe in “home sampling” where a kit is sent to an individual’s home for them to take a sample, which is sent through the postal system to an accredited laboratory to carry out the “test”.
Trouble for Superdrug’s £69 test
In the last week there was a much publicised release by Superdrug of a £69 at home kit, that is performed in the accredited The Doctors Laboratory pathology lab. The difficulty arose on Thursday when Abbott, who manufacture the system that the test is performed on, released this press release stating that it is “unable to give any guarantees or make claims for the performance of our test if it is used with finger stick blood,” as typically collected in home sampling kits. The validation work that underpins their product’s FDA Emergency Use Authorisation (EUA) and CE marking was performed using “venous” blood and blood taken from blood banks, and performed in a clinical setting.
Abbott does note that “it is the responsibility of the individual laboratory to determine specific specimen stability criteria for their laboratory per their laboratory workflow.” The Doctors Laboratory has performed independent verification of the Abbott product, however, it is unclear whether home sampling was part of the verification protocol.
This avenue of testing was finally closed today when MHRA requested that all “finger prick” testing in the UK must stop until this sampling method is validated further.
Is at home sampling a valid solution?
The main point here is that the validation work that the manufacturer performed was done in clinical laboratory environments, and not in homes. In clinical settings blood is typically taken from blood banks, or using “venous draw,” taking blood from a vein in your elbow. Home testing throws up further complications, such as the need to send the sample through the post where it experiences a range of environmental conditions. We know this can have impact. In the manufacturer’s guidance for the Roche Elecsys Anti-SARS-CoV-2 assay it states that samples were stable for 3 days between 15-25°C and in the Abbott SARS-Cov-2 IgG guidance it states that the maximum sample storage time at 15-30°C is 2 days.
This means that the viability of this type of home sampling might be dependent on where you live (and thus the postal system available to you). The US postal system can often take 3+ days end-to-end, but the UK has an often overlooked superskill, in that we do have a very effective national mail carrier in the Royal Mail, that provides one of the most ubiquitous next day collection and delivery services of any country in the world. This is an asset that the UK should fully utilise to widen the envelope of high accuracy testing in order to manage the pandemic going forward.
The future for home testing
Testing for All believes that laboratory testing will remain the highest quality COVID-19 testing for a period of time, while other technologies such as lateral flow and other innovative diagnostics such as DNANudge mature to reach the bar of >99.5% sensitivity and specificity suitable for surveillance use cases where the prevalence of SARS-CoV-2 is low.
Our current approach to testing
At this time Testing for All will continue to perform antibody tests for healthcare workers and employers across the UK using “venous blood” draw sampling, with tests carried out on the Abbott IgG immunoassay. We will also continue to offer PCR swab based testing specifically for employers who are not able to wait for a slot to become available on the NHS testing service. If you are an employer who needs this service for your employees, please contact us.