How does lateral flow testing work?

In an effort to combat rising infection rates, residents of the UK have been advised to take two lateral flow tests per week. This express test takes mere minutes to produce a result. However, some experts have called the efficacy of these results into question, citing a lack of accuracy as the primary issue. What are lateral flow tests? How accurate are their results? For the answers to these questions and more, read on to discover everything you need to know about lateral flow testing.

What is a lateral flow test?

A lateral flow test is used to detect the presence (or absence) of a known pathogen or genetic marker. The test is suitable for humans or animals. Through the use of a simple diagnostic device, the results of a lateral flow test provide the quickest way to confirm any detectable pathogen or marker. Rapid pregnancy tests are the most common form of lateral flow tests available. Express tests are used in a wide variety of industries though, thanks to their versatility and ease of use. For example, lateral flow testing can also detect contaminants in the environment, such as water supply contamination, food items bacteria, and animal feed infections.

Despite finding themselves under the spotlight recently, lateral flow tests are far from new development. They’ve been used in various fields of medicine for many years. Lateral flow technology is so widespread that different industries and different countries call it by different names. The most common terms you may find are express test, dipstick, rapid test or quick test. Depending on where you are in the world, medical experts may call a lateral flow test a lateral flow immunoassay, or a lateral flow immunochromatographic. The name will always depend on the specific country’s established naming method.

Why is lateral flow testing effective?

Lab tests for COVID-19 are extremely effective and boast a high rate of accuracy. However, they take much longer than a lateral flow test to produce results and are a lot more expensive in comparison. Lateral flow tests require no lab equipment. Mass testing of any population is a costly investment and, because of this fact, lab-based testing methods are simply impractical on a large scale, particularly when regular testing needs to be a priority.

According to numerous experts, asymptomatic infections account for the majority of COVID-19 cases. It should go without saying that undetected infections accelerate the spread of any virus. In order to solve the aforementioned problems as effectively as possible, the UK Government has decided that lateral flow tests are the most efficient and cost-effective solution.

We can’t help but agree with this methodology. Thanks to the ease with which these tests can be administered, the mass roll-out of testing kits across the UK has largely been a successful endeavour. Without the need for lab equipment to achieve results, lateral flow tests are quicker, cheaper, and above all, much more scalable than the majority of alternative tests. Compared to tests that require lab equipment, the slight decrease in the accuracy of results is worth the ability to test a mass population, twice a week if necessary; which is exactly what we’ve witnessed happening in the UK.

How do rapid tests work?

Lateral flow tests use control lines and test lines to indicate the result of any targeted antigen, pathogen, or genetic marker. In the case of COVID-19, for example, the control line acts as a guard against skewed results, while the test line is the primary indicator of whether a test subject is infected or not. The test line is able to indicate this due to the diagnostic device being set up to specifically detect COVID-19 antigens.

The first step of a lateral flow test is to gain a biological sample. A cotton swab is the most common instrument used to attain a sample. Once a sample has been taken it must be placed directly on the lateral test diagnostic device. Through the use of an absorbent pad, saliva or mucus of the subject is passed through a micro-filter, where nanoparticles, antibodies, and a nitrocellulose membrane work in combination to analyze the sample. After roughly 30 minutes of exposure to the sample, the lateral flow device will either produce a negative, positive, or failed result.

It’s important to remember that no test is 100% accurate. There is always the potential for a false reading, regardless of how effective the test in question may be. What this means is that even if a rapid test result for COVID-19 comes out as negative, that’s not a definitive answer as to whether you’re infected or not. Instead, these tests provide a reliable-enough indication of the presence of an antigen in any given population.