It's emerged that some letters sent to patients in the northeast whose medical files are being re-examined by the Health Service Executive were posted to the wrong addresses.
A company was employed by the HSE to send the letters to four and a half thousand patients informing them of the review.
The HSE has apologised to those involved and says it has arranged for the correct information to be re-sent this evening.
The HSE decided to re-check the files of 4,500 patients after it emerged that a locum consultant radiologist may have missed a number of abnormalities in chest x-rays and CT scans.
The radiologist worked at Our Lady of Lourdes Hospital in Drogheda and Our Lady's Hospital in Navan in 2006 and 2007.
The executive employed an outside company to help it arrange that letters would be sent to all of the patients involved and on Tuesday the letters were sent.
The executive said it is deeply disappointed and has expressed its sincere apologies.
It has arranged for the correct information to be resent to all patients this evening.
While the Data Protection Commissioner has also been informed.
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