Reflections on Covid Testing (3). Lateral Flow Testing : The Good, the Bad and the Ugly

Reflections on Covid Testing (3). Lateral Flow Testing : The Good, the Bad and the Ugly

These posts reflect the personal view of Adrian Walsh

Although lateral flow testing was considered a great success in mitigating the spread of infection during the Covid pandemic, it had its detractors, mainly due to its perceived poor sensitivity compared to PCR testing.

My personal view was that the technique was very useful but had three distinct facets. Using the title from a well-known Western movie genre, these facets could be described as the Good, the Bad, and the Ugly.

The Good was that these tests were simple, rapid (15 minutes), cheap, and could be self-administered.

The Bad was that as they were not as sensitive as lab tests, they could not detect infection in the first 4 days post-infection. This gave people the impression they were negative, when in fact they were false negatives. Repeated daily testing would resolve this issue.

The Ugly was that many people, were unsure if a very faint pink T-line on a white background was a true positive. Borderline positives required consultations with family members or holding up cassettes to the light from a window for more assurance. The trouble really was that originally the tests were designed for professional administration and analysis. Self-administered tests at home were analysed subjectively and often erroneously.

On balance, knowing these limitations, the use of lateral flow tests during the pandemic should be considered a success.

On the subject of Western genre film titles, as a metaphor for other aspects of pandemic testing, there may be some mileage in “A Fistful of Dollars” and “A Few Dollars More”, but I will leave that up to your imagination.