As demand for rapid antigen tests (RATs) reaches fever pitch, a Fair Go investigation has found they may not be as accurate as stated.
Dr Gary Payinda told Fair Go a RAT can provide false negative results, especially when people are in the early of late stages of infection.
"The time when it's less accurate is when you are asymptomatic - not feeling symptoms - and you test yourself just to see and in that situation, it will be it wrong 20 to 30 per cent of the time."
The tests boast accuracy rates in the high 90 per cent but Payinda says this is mainly when the patient is symptomatic.
"It will do a good job of isolating the worst of the worst and identifying them, but it doesn't do much more than that," Payinda says.
The Government is now handing out RATs to household contacts as Covid-19 surges through New Zealand. Payinda says the tests can give people a false result, meaning they head out into the community with Covid-19.
"It will likely give you the wrong answer two or three times out of every 10."
The Ministry of Health told Fair Go it's confident in the efficacy and accuracy of its tests.
"The Ministry of Health and ESR continue to only approve tests that meet a very high threshold for quality to reduce the number of false positives and negatives," a spokesman told Fair Go.
READ MORE: Why RATs can show negative when you're feeling symptoms
As sales of RATs spike around New Zealand, Payinda says if you are going to spend money on keeping safe from Covid, he recommends a different purchase.
"As long as we understand the limitations of RATs in asymptomatic people and we use masks, do vaccinations and boosters and we think about indoor ventilation, we'll be alright."
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