Dr Nathan Hudson-Peacock says there is a testing ‘interpretation window’ of usually 30 minutes, but leaflets that come with the kits should be double-checked to make sure to make sure
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A warning has been given by a doctor over faint lines appearing on lateral flow tests.
Each testing kit has an “interpretation window” and each result should be checked within this time to ensure they are accurate.
Dr Nathan Hudson-Peacock says this window is usually 30 minutes, but leaflets that come with the test kits should be double-checked to make sure it is accurate and within the time frame, reports the Liverpool Echo.
A line next to the ‘C’ means the test has worked, as the C stands for ‘control’, but a line next to the ‘T’ (test) indicates a positive Covid reading.
Dr Nathan Hudson-Peacock told ChronicleLive “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 says close contacts of those with covid should do daily lateral flows (LFTs) for seven 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.