The rumors are swirling: can lemon juice, or even your favorite soda, lead to a false positive on a COVID-19 test? It sounds like something out of a movie, but there’s some truth to it. Let’s dive into the science behind this phenomenon and understand what’s really going on.
The Viral Trick: школьникs and Soft Drinks
During the height of the COVID-19 pandemic, reports emerged of школьникs in the UK using soft drinks to manipulate at-home COVID tests. The goal? To skip class by feigning a positive result. This sparked investigations into whether common beverages could indeed influence test outcomes.
How Lateral Flow Tests Work
To understand how lemon juice or soda can cause a false positive, it’s important to know how lateral flow tests (LFTs) function. These tests are designed to detect the presence of a specific substance in a liquid sample.
- Pregnancy tests look for a specific hormone.
- COVID-19 tests identify a protein found in the SARS-CoV-2 virus.
The Soda and Soft Drink Study
A 2021 study published in the *International Journal of Infectious Diseases* explored whether various beverages could cause false-positive results on COVID LFTs. Researchers tested Coca-Cola, other sodas, energy drinks, vodka, whiskey, and brandy. The results were surprising: many of these liquids produced false positives when applied directly to the test without the buffer solution. Another study in 2021 found similar results with sodas and non-alcoholic soft drinks.
The Acidity Factor
So, what’s the magic ingredient? The answer seems to be acidity. Drinks like orange juice, cola, and apple juice contain citric acid, phosphoric acid, and malic acid, respectively. These acids give the beverages a low pH, typically between 2.5 and 4. This level of acidity can disrupt the function of the antibodies used in the tests, which are designed to work in a neutral pH environment like that of the bloodstream (around 7.4).
Lemon Juice and COVID Tests
Given the acidity of lemon juice, it’s plausible that it could also cause a false positive on a COVID test. Lemon juice has a pH of around 2, making it even more acidic than many soft drinks.
Important Considerations
- Not all tests are affected: It’s important to note that not all lateral flow tests will react the same way to acidic substances.
- The buffer solution matters: The buffer solution that comes with the test is designed to maintain the correct pH and ensure accurate results. False positives are more likely to occur when the test is used incorrectly, without the buffer solution.
- False positives don’t indicate test reliability: Getting a false positive by misusing the test doesn’t mean the test is unreliable when used correctly.
Real-World Implications
These findings have real-world implications, especially for settings where frequent testing is required, such as schools and workplaces. To minimize the risk of false positives:
- Test in the morning: Perform LFD testing first thing in the morning, before consuming any food or drinks.
- Follow instructions carefully: Make sure to use the buffer solution and follow the test instructions precisely.
- Supervise testing: When possible, testing should be supervised to prevent misuse.
Beyond COVID Tests: Other Lateral Flow Tests
The phenomenon of false positives due to acidic substances isn’t limited to COVID tests. There is evidence suggesting that other lateral flow tests, such as pregnancy tests, can also be affected.
The Bottom Line
While it may be tempting to try and “hack” a COVID test with lemon juice or soda, it’s not a reliable way to get a fake positive. Misusing tests can lead to inaccurate results and undermine efforts to control the spread of the virus. Always follow the instructions carefully and use the provided buffer solution to ensure accurate results.