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23-11-2020
A day in the life of a PCR Antigen test
ARTICLES

From Swab to Lab to Result


The quest to find a viable rapid test solution for mass asymptomatic screening is ongoing. Early results from the Liverpool pilot report, which was conducted in November '20, saw the Innova lateral flow device as missing between 22% and 41% of PCR positive cases: and so, we are certainly not there yet when it comes to Rapid testing solutions. As such, most employers investing in workplace testing continue to choose the gold standard lab-processed PCR method to keep their workforce safe and operational.


The Journey - From the workplace to the lab


Most organisations offering workplace screening engage Occupational Health specialists to manage operations on the ground. As trained healthcare professionals, OH specialists are experienced in setting up testing zones according to strict safety protocols, supervising staff to self-swab correctly and ensuring accurate recording of samples.


As samples are taken and logged, the OH specialists pack them using a 3-layer system.  This is to ensure a greater degree of safety and if any leakage was ever to occur, the 3 layer system of safety means that 1 leak alone wouldn't contaminate other samples.  The samples are then shipped to the lab. 


At the lab


Once they have been unpacked and registered on the lab's information management system, samples are opened in a sterile space and essentially 'washed' in order to isolate and extract any RNA that may be present. A mix of enzymes and chemicals is then added in order to produce DNA 'copies' of the RNA. The samples are now ready to be loaded onto plates for PCR processing. This is a delicate process which requires a high level of skill and precision.


Having been set up to detect specific parts of the SARS-CoV-2 genome, the PCR machine cycles the test temperature typically 40-45 times to produce exponential amplification of any DNA present. At the end of each cycle, a probe is inserted to check samples for  virus presence. The heavier the viral load (the more SARS-CoV-2 virus in the sample), the greater the number of copies that are produced and the sooner virus presence will be detected. It is the level of amplification, i.e. the large number of  cycles which allows PCR to detect such a broad range of infection stages: this is particularly salient in a routine screening context which aims to catch early-stage infection, thereby reducing or eliminating the chance  it will be passed on to others.


Once the PCR test is complete, the lab's analysts collect and review results, troubleshoot any issues and transfer final results back into the lab's systems. The lab then reports results to PHE and produces any additional documentation, e.g. fit-to-fly certification - that has been requested.


Results are returned to the workplace


Typically results are returned to Occupational Health specialists who are then responsible for communicating them back to the business and they are then often on on hand to provide advice, discuss any queries with the lab and offer support to employees where needed, especially where positive cases may have then been reported.


Since the start of the Coronavirus pandemic our network of labs have delivered testing across a wide range of contexts and scales, from small-batch routine testing of particularly at-risk employees through to organisation-wide programmes. All labs have been through the Department of Health and Social Care's rigorous approval process for Covid-19 testing.


They are staffed by highly skilled scientists and lab technicians and are experienced in turning around accurate, reliable results within 24 hours. If you want to learn more about how we can support your workforce testing, just contact our Head of Account Management, Ami Jayakrishnan 



 

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