Since SARS-CoV-2 was first sequenced in January 2020 the testing market has burgeoned. Few people realise no mass tests look for the actual virus – each test looks for different components of the virus.
PCR was the first available test and is often referred to as the ‘gold standard’. This is something of a misnomer as other assays now available are as accurate as PCR (‘accuracy’ is defined here). PCR has disadvantages. It’s expensive, needs a lab and highly-skilled technicians and time to result critical in terms of infection control it has a far greater impact on outcomes than incredible sensitivity figures.
||Highly sensitive and specific, detects low levels of viral material so widely accepted by Governments for travel etc.
||Needs professional lab technicians to and a lab. Can still give a positive result long after infection has cleared. Very expensive. Takes 24-72hrs.
||Point of care / need so can be used outside a lab. About an hour.
||Needs professional lab technicians to operate. Can still give a positive result long after infection has cleared. Quite expensive.
|LATERAL FLOW ANTIGEN
||Cheap – £5-10 per test, no specialist staff required. Rapid – 15-30mins
||Only identifies people with the highest viral loads so a negative result does not guarantee you are not infected or not infectious.
NB Antibody testing only picks up previous infections, not current ones.
If we summarise the choices, until now the options have been:
PCR which is highly accurate but takes time to process and is expensive;
LAMP which can be used point of care but is technically more demanding than people had thought;
LFDs which are simple, cheap and rapid – but lack diagnostic power.
Current LFDs have been promoted by government as suitable for identifying the infectious and do have their uses – as a rapid aid in clinical diagnosis of a symptomatic patient, or in public health screening and large-scale public testing. But in trials they identified as few as 30% of the people who tested positive on PCR.
The AFS-1000 COVID-19 Cassette can pick up a current infection with accuracy on a par with PCR and LAMP in 15 minutes.