With many of us regularly using lateral flow tests to minimise the spread of coronavirus, there has been some confusion over interpreting the results.
After following the instructions on the leaflet included with testing packs, there's often a clear result.
A line next to the 'C' on the test simply means the test has worked, with the C standing for 'control', while a line next to the 'T' (test) indicates a positive covid reading.
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But an A&E doctor has issued some guidance to help people understand what a faint line can mean.
Dr Nathan Hudson-Peacock, from London, took to his Instagram page to explain.
He said each testing kit will have an interpretation window, usually 30 minutes but you can check the leaflet that comes with the kit to make sure.
You should check your result within this time period to ensure it is accurate.
His post continued: "Essentially, if *any* line appears before the end of the interpretation window 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."
He also reiterated NHS guidance, which states anyone with symptoms should isolate and book a PCR test, regardless of lateral flow result.
Dr Hudson-Peacock continued: "If the faintly positive line appears after the time window, the most likely cause is either that there has been some contamination (e.g. food or drink, or some other very weak contaminant that is causing a false positive), or there are just incredibly low levels of the virus.
"If it is the latter, and obviously assuming you are asymptomatic at this point, then you are very unlikely to be a transmission risk anyway and so it is of little significance.
"Therefore, the most sensible next step, in my opinion, is not to isolate unnecessarily and not to book a PCR (makes it harder for people who genuinely need them to get one), but to be extra careful with precautions (social distancing, hand washing and mask wearing), and to continue testing with [lateral flow tests] as per NHS guidance."
NHS guidance states:
• Close contacts of those with covid should do daily lateral flows (LFTs) for 7 days if both asymptomatic and fully vaccinated, or asymptomatic and aged 18 and six months or under
• If not a close contact, then you should do a LFT before mixing with people indoors and before visiting someone who is at higher risk of getting seriously ill from covid.
If you have symptoms, you should isolate and book a PCR, even with a negative LFT.
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