I’m a doctor and here’s how Coke can give a false positive lateral flow
TAKING lateral flow tests is a great way to protect those around you from coronavirus.
But as the pandemic has gone on, people have decided to do experiments on the tests, leaving many confused when they then show a positive result with different liquids.
Taking to Instagram, one doctor explained why liquids such as cola and citrus really show a positive line on a lateral flow test.
NHS doctor and nutritionist Dr Joshua Wolrich, explained that the solution you put the swab into after it’s been in your nose/throat is what’s known as a buffer solution.
He explained: “It has a controlled pH that allows the test to work accurately.
“Pouring any other sort of liquid without controlled pH (tap water, coke, etc) on the test is completely and utterly pointless.
“If it comes up with two lines after that, it’s not proof that the test has always been pointless or whatever nonsense the anti-vaxxers are claiming.
“It’s simply a visual representation that medical tests are only valid when the instructions are followed and the pH of your solution is giving you a meaningless result.”
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When it comes to detecting the bug in adults, previous studies have shown that the tests are over 80 per cent effective at detecting any levels of the virus.
The paper, published in Clinical Epidemiology found that the test detected 90 per cent of infections when people were most infectious.
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The UK Health Security Agency also previously found that lateral flow tests are as effective at detecting Omicron than other variants before it.
If you test positive then you must isolate in order to stop the spread of the bug, but if you haven’t got symptoms you might be worried about getting a false positive.
People having been taking lateral flows now for well over a year due to the pandemic and it’s important that you always read the instructions that come with tests and many are manufactured in different places, so you might have to do them differently.
One of the main instructions on most packs though is that you should wait 30 minutes after eating or drinking to take the test.
This is due to the fact that some foods and drinks, such as water and fizzy pop, can interfere with the test.
ALL IN THE PH
Dr Karan Raj explained that to understand why lateral flows give positive results with different liquids, you need to look at the test itself.
He said: “The grey box and the portion just above it contain antibodies that are sensitive to the Covid-19 virus.
“If you use things like soda, tap water and fizzy drinks, that’s going to provide an altered pH, which will affect the function of the antibodies on the test line.
“That is why you need to use this buffer solution (consisting of 99.7 percent saline solution) which provides a stable pH that will actually make the test work.”
Lateral flow tests are an easy way to detect Covid fast and it was last week announced that some people testing positive with Covid will no longer need to take a follow up PCR test due to how wide spread the virus now is.
While cases are wide spread across the country, most people catching Omicron say there are experiencing symptoms similar to a common cold.
A string of hugely positive studies show Omicron is milder than other strains, with the first official UK report revealing the risk of hospitalisation is 50 to 70 per cent lower than with Delta.
The full list of reasons to get a PCR test
In England, the reasons for ordering a PCR test are:
- You have Covid symptoms
- You’ve been in contact with someone who’s tested positive and you must self-isolate
- You’ve been asked to get a test by a local council or someone from NHS Test and Trace
- A GP or other health professional has asked you to get a test
- You’re taking part in a government pilot project
- You’ve been asked to get a test to confirm a positive result
- You’ve received an unclear result and were told to get a second test
- You need to get a test for someone you live with who has symptoms (you can order tests for up to three household members)
- You’re in the National Tactical Response Group
- You are due to have surgery or a procedure (in some occasions)
Exceptions to the lateral flow test rule:
- People who are eligible for the £500 Test and Trace Support Payment (TTSP) will still be asked to take a confirmatory PCR so they can access financial support
- People participating in research or surveillance programmes may still be asked to take a follow-up PCR test
- Around one million people in England who are at particular risk of becoming seriously ill from Covid are involved in new research of treatments
Covid booster jabs protect against Omicron and offer the best chance to get through the pandemic, health officials have repeatedly said.
The Sun’s Jabs Army campaign is helping get the vital extra vaccines in Brits’ arms to ward off the need for any new restrictions.
As well as jabs, regular testing has become a way of life for Brits.
Experts have previously also explained why a faint line could also be a false positive.
Posting a photo of a vaguely positive lateral flow to Instagram, London-based A&E doctor Nathan explained what it could mean.
He said: “Essentially, if *any* line appears before the end of the interpretation window (check leaflet, usually this is 30 minutes), then this is a *positive* test and you must isolate and book a PCR.
“However, if a line appears *after* the interpretation window then this does NOT count as a positive test. You do not need to isolate and you do not need to book a PCR.”
But if you have symptoms, regardless of the lateral flow test result, you should isolate and book a PCR test.