The HSE has confirmed that around 11,500 women have been affected by a Cervical Check testing problem between 2015 and last year.
A review was ordered after an external lab highlighted a problem with the use of out-of-date testing kits for the HPV virus.
The HSE says there is no reason to check women who had tested positive on the original out-of-date test, but around 5,000 women from the original group have been asked back for re-checks.
However it says the clinical risk to women's health is low and the re-tests are precautionary.
The recent IT problem - which is separate to the out-of-date testing issue - resulted in late results for around 800 women.