Latest flow test kits for Covid-19
There are now three types of lateral flow tests for Covid-19 available. With official Covid testing now moving towards rapid on-site lateral flow methods and away from reliance on laboratory PCR methods, it is a good time to consider the various types of COVID-19 test kits, and how they can be useful for workplace, healthcare and self-testing for the infection.
SARS-nCOV-19 now called COVID-19 continues to be a high frequency infection in the adult UK population, with infection seemingly still occurring in exposed but vaccinated individuals, and prevalence seems likely to increase further during the winter months as it did last year.
COVID-19 antibody test kits
The original Covid-19 lateral flow tests were blood tests for antibodies produced after exposure to the virus. They did not screen for the actual virus. The early tests retrospectively had very good levels of accuracy, specificity and selectivity, but failed to meet the expectation of offering accurate screening for the active Covid infection, due largely to the variance in time taken for the antibodies to be detectable.
With the prevalence of vaccination, the use of antibody screening tests has now moved to determining if booster vaccinations are needed (1), and with a smaller role in screening individuals who have not received vaccination for natural post exposure antibodies, ie answering the simple question have I had COVID-19 in un-vaccinated individuals as part of a risk assessment for employment roles involving an element of COVID-19 exposure risk.
(1) The introduction of a LOD (level of detection) cut off in certain Covid-19 antibody lateral flow tests enables a call to be made if blood antibody levels are high enough to offer protection against exposure.
COVID-19 antigen test Kits
In 2020 lateral flow rapid test were developed which screened for the actual virus surface protein in samples taken from the upper naso-pharynx. For the first time it was possible to take a nasal swab and detect COVID-19 infection in under 15 minutes. These covid antigen test kits remain the best way to detect the virus other than with a PCR test, in the right hands, but getting a good quality high nasal, or naso-pharyngeal sample is unpleasant to say the least. While some of these lateral flow Covid tests became listed for self-testing, the concern remains that without an adequate sampling procedure, the Covid test kits risk giving false negatives, due to the lack of collected virus.
Covid-19 antigen saliva test kits
Manufacturers became aware of the sample collection being critical to the perceived accuracy of their product and in 2021 the first saliva only COVID-19 test kit was launched. This design avoids the need for any swabs and the donor simply has to cough 3 times and then produce an oral saliva sample which offers COVID-19 screening with and overall accuracy of over 97%. The saliva covid test kits are currently only available as home test kits.