The Department of Health has said the error which lead to 100 people getting an incorrect test result occurred due to an "IT glitch".
It comes as Ireland has recorded its highest daily death toll of the Coronavirus pandemic as the virus claims a further 41 people.
There have now been 406 COVID-19 related deaths in Ireland, with 11,479 confirmed cases.
Testing remains a focus for the Department of Health, who were forced to apologise after 100 people received an incorrect test result.
Patients had been advised, in error, that their test did not detect Covid-19, and on review were found positive for Covid-19.
The Department of Health said the error occurred due to an "IT glitch".
Irish patient samples, which had been sent to a laboratory in Germany in order to tackle the state's backlog in testing, had been sent back as "invalid".
Deputy Chief Medical Officer, Dr Ronan Glynn, paid tribute to his colleagues in Germany before explaining that some tests can be reported as "indeterminate or invalid".
Around 100 Irish tests received this result, which the IT system in Ireland did not recognise and reverted the results to negative.
These results were then incorrectly communicated to patients.
The Department of Health said all the cases have been identified and the IT issue has been rectified.
"We'd like to reassure members of the public that this is not a testing issue but an IT glitch on our side," Dr Glynn said.
Over the past week, 20,468 tests were carried out in Irish laboratories and of these 4,233 were positive, giving a positivity rate of 21%.
Concerns continue to grow over the effect of the pandemic on nursing homes as the deadly virus continues to target elder patients the hardest, with a median age in the reported deaths of 85, 31 of these had underlying health issues.
Dr Tony Holohan, Chief Medical Officer says that it is possible that some people who have died in nursing homes or other locations, did not receive a test and will not be counted in the official COVID19 figures.
187 deaths have been reported by nursing homes, with over 150 clusters identified.
Dr Holohan says he "remains concerned about the prevalence of COVID-19 in nursing homes and residential care settings".
After a meeting between stakeholders, the National Public Health Emergency Team and Health Minister Simon Harris yesterday, the HSE are putting in place a coordinated national process to identify the prevalence of the virus in residential healthcare settings; as recommended by the ECDC, including targeting homes who have not recorded any cases of the virus in an attempt to preempt any further spread.
Nursing Homes Ireland (NHI), which represents more than 300 private nursing homes, say a lack of priority placed on nursing homes in the early stages of the outbreak has contributed to the issue.