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.
| Test | Advantages | Disadvantages |
|---|---|---|
| PCR | 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. |
| LAMP | 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.