The health products regulator says it's investigating reports of false positive COVID-19 test results from Genrui brand antigen tests.
Genrui is one of the most common and cheapest brands of antigen tests available in Ireland.
The tests are sold in several large retailers and supermarkets, including Lidl.
However, there have been a number of reports on social media about the tests in question returning false positive results.
Cork paediatrician Dr Niamh Ni Loinsigh highlighted the issue over the weekend, saying she'd received "100s of messages" about the brand in question.
Received 100s of messages through my Insta about Genrui antigen tests.
When pcr was available there seemed to have been lots of false positives with these kits.
This could have major implications for people now with no pcr available.
Have you had any issues with them? pic.twitter.com/hmMgGz8hFp
— Dr Niamh Ni Loinsigh (@niamh_dr) January 1, 2022
She said the issue "could have major implications for people now with no PCR available".
In a statement, the Health Products Regulatory Authority (HPRA) said it had received a "number of reports" about the potential issue.
They said: "The HPRA is following up with the manufacturer of the test to investigate the matter and will also liaise with other European Competent Authorities in relation to this issue.
"We would encourage individuals who have experienced a false positive or negative result to report the occurrence to the HPRA at devicesafety@HPRA.ie."
It says rapid antigen tests do have the potential to return false negative and false positive results, noting "it's widely acknowledged that rapid antigen tests are less accurate than PCR tests and should be used in line with current public health guidance".
Genrui tests are manufactured by Genrui Biotech in China.
Like many such tests, people using the rapid test are encouraged to look "very closely" for a line indicating a positive result - with the manufacturers noting the line can be "very faint".
The tests are approved for use in the EU, with the European Commission noting tests have shown they have a 91.15% sensitivity.
Antigen tests have been used much more widely in Ireland in recent weeks, with people aged 4-39 now being asked to do a rapid test before seeking a PCR.