Lateral Flow Testing – Rapid Covid-19 tests
Many of us have by now experienced PCR swab tests taken from the throat and nose which are sent off to the laboratory to look for SARS-CoV-2 viral genetic code (RNA). At present, these are the most accurate available tests for confirming the presence or absence of Covid-19 infection.
Rapid testing or ‘lateral flow’ tests have been launched in the UK and over 130 local authorities have signed up to the initiative. The aim is to target asymptomatic testing in individuals such as critical workers and those who have to leave the home for essential reasons, in order to identify symptomatic cases and break the chain of transmission.
The Medicines and Healthcare Products Regulatory Agency, which initially deemed the Innova test not fit for use among asymptomatic people in the community, changed its guidance on 23 December 2020.
So far, the test, which can provide results within 30 minutes, has helped to identify over 14,800 cases of infection that would have gone unrecognised.
The results from Liverpool
A pilot of community rapid testing was conducted in Liverpool and the test identified 8,300 people in the region with Covid-19. The report, however, did not find any clear evidence yet that the testing in Liverpool had any effect on numbers of Covid-19 cases or hospital admissions.
However, there is also concern amongst scientists that the tests are too inaccurate and negative results could falsely reassure people and thus increase the virus’s spread.
In the Liverpool pilot study, the test missed infection in 60% of people and it also missed 30% of cases in people with very high viral loads.
The Cochrane Collaboration’s* lead on Covid -19 test evaluation, Jon Deeks, has said that results from government studies have been selectively reported and some have not been reported at all.
He has expressed concern that the UK government is widening the rollout of the Innova lateral flow test without supporting evidence and that this may cause serious harm.
The limits of the tests
Whilst we await more independent evidence of the benefits and accuracy of the lateral flow testing, it is important for us to consider its use within its limitations.
For now they should be considered as a ‘red light’ test – if they come up positive you are potentially infectious to others and you must self-isolate.
However, they are not ‘green light’ tests i.e. if your test is negative you cannot be certain you are not infectious and you must continue to take the usual precautions.
Dr. Sidra Malik BMBS MRCGP DRCOG DFSRH
9th February 2021
* Cochrane is a global independent network of researchers that gather and analyse the best available evidence to help people make informed decisions about health and healthcare.
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