A cervical screening blunder involving women in the North Western Health Board area has resulted in the recall of more than 2,000 smear tests.
Almost 70 women are to be informed by their family doctors that the results of their tests, carried out in 1997 and initially reported as normal, were in fact abnormal.
A health board spokeswoman said last night that the errors occurred when work was given to a private laboratory, after a backlog developed at Sligo General Hospital in late 1997.
A subsequent audit of the tests by the hospital discovered that there were significantly fewer than expected abnormal smears identified. "A total of 68 tests were incorrectly reported to us by the external laboratory," she said.
All of the women affected have not yet been informed, but the spokeswoman said they will have been made aware of the situation by their general practitioners by noon today, before a press conference is held by the health board to outline the details of the case.
The Sligo Labour Alderman, Mr Declan Bree, has called for a full investigation and said new quality-control procedures should be introduced immediately.
The errors in the 1977 tests were only discovered in January of this year. The women involved had received the initial results between February and June of last year.
All of the tests involved were independently re-screened. The corrected results received last week showed that a total of 68 results were in error.
A briefing note distributed by the health board to general practitioners states that the re-screening "revealed that 13 women had been incorrectly informed that their cervical smear was normal when in fact there was moderate or severe dyskaryosis present".
A further 53 women would need to have repeat smears carried out because of borderline or mild changes, it said.
Last night medical sources explained that moderate or severe dyskaryosis was a pre-malignant condition which would need to be monitored but would not mean that disease was present.
Sources stressed that the risk of it progressing to cancer over that time period was very low.
The health board said that for most of the women it was extremely unlikely that there will be any long-term implications, with medical experts confident that any problems identified would be treated successfully. The development rate for any relevant conditions is generally between 10 and 15 years.
The North Western Health Board Director of Public Health, Dr Sean Denyer, said he "deeply regretted" the anxiety caused and said it was "very important" that the women "availed of the various procedures to guarantee that they are reassured as soon as possible".
He said the women were now receiving the correct results, "which they should have received a year ago". A help-line has been set up on 1800 200180 between 9 a.m. and 7 p.m.