Image copyright Getty Images Image caption Three calls to the consumer complaints helpline within the hour
Home diagnostics kits which deliver false positive readings on routine home tests could be sold a second time by British stores.
The warning follows “mystery shopper” tests which found that more than a million kits had already been sold.
Some manufacturers had experienced false positive readings while others were testing incorrectly, the Food Standards Agency (FSA) has warned.
Lidl is to stop selling the kits.
Ofcom estimates that the technology provides for 3% of testing.
Having contacted three consumers within the hour who had faulty kit, Ofcom is also advising consumers not to use these products.
Nearly 1 million kits, including Anglia and Tesco, were sold by Warranty Direct before Christmas.
Three false positives from three products from four manufacturers were found in the “mystery shopping” tests – although some of the false positives could be down to the packaging, the safety warning said.
Other faulty readings included Carmax and Whiteware.
Image copyright BT All tests between the correct results and false positives were recorded on the pages of the browser’s The Chartered Institute of Environmental Health (CIEEH) e-toolkit
The test, a screen that forwards a written question in multiple choice answers to a company’s site, was provided to retailers who had suggested there might be problems with devices they had made available.
Common queries included “what are the results of the test and do you perform a home test?” and “is it safe for me to dispose of it?”
After checking each firm’s site, several of the companies issued a “technical warning” and said: “We are sorry for any inconvenience”.
But the regulator warns that consumers with suspect kits should not use them.
“These findings highlight the importance of our ongoing investigation and will mean a review of use of this device at UK retail outlets,” said Helen Holland, Ofcom’s director of technical standards.
“The devices involved appear to have been manufactured within reasonable time limits and the level of errors appears to be within acceptable levels.
“In the meantime, consumers should use appropriate and authorised devices and appliances.”
Lidl has stopped selling the kits by Warranty Direct because “it would not be prudent to continue to trade those types of products at this stage,” a spokesman said.
“Whilst we do not know how many other retailers have sold such products, we will temporarily stop ordering those products and checking them before re-ordering.
“Whilst we are hopeful we will be able to resume stock orders shortly, this is unlikely to be within the next week.”
Sainsbury’s had previously said it would withdraw all ten of the firms’ products but will be reviewing the situation before selling them again.
Anglia, Tesco, Morrisons, the Co-op, Dunelm, Sainsbury’s, Waitrose, Waitrose Direct, Poundworld, Debenhams, Poundstretcher and Poundworld Direct have since removed them from their internet platforms.
The technology “isn’t nearly as good as we want it to be and it is far too difficult for consumers to get to the bottom of the problem”, said Iain Neale-Hair, chief executive of IMI, a testing lab.
“Up to now the testing kits have shown a genuine failure rate of 0.4% to 1%. But while I am unhappy with the false positives on the home kits, it seems that some kits are starting to show a false positive rate of up to 40%.
“We can see the hope of these types of devices being useful to patients being short-lived. This is a significant flaw for a technology which had promise to deliver a revolution in home testing for diseases.”
In the United States, the FDA has fined seven manufacturers a total of $5.6m (£4.2m) for false positive readings.
But the agency says there have been no similar problems in the UK.
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