The Western Health and Social Care Trust has asked 86 women to arrange a repeat cervical smear following a review of number of tests done between April and June 2018.
A cervical screening is a way of detecting abnormal cells in the cervix.
Finding and removing abnormal cells early can help prevent cervical cancer.
Women aged 25 to 64 who are registered with a GP are automatically invited for cervical screening.
The Trust's medical director Dr Dermot Hughes said the repeat test is a precautionary measure and he apologised for any worry or inconvenience caused.
This review was carried out after differences in the reporting of a number of tests were found during routine performance checks conducted at the Trust's pathology laboratory.
The Western Health Trust said it set up a review team, alerted the Public Health Agency and Department of Health and began the review process.
As a result of the review, 86 women have now been contacted by letter asking them to arrange repeat smear test with their GP.
Sixty-one of the women are from the Western Trust area, eight from the Belfast and South Eastern Trust areas and 17 are from the Republic of Ireland.
Dr Dermot Hughes said: "The women affected will have received letters inviting them to contact their GP to arrange a repeat smear test.
This does not necessarily mean that the results of their initial test was wrong; the repeat test is a precautionary measure to provide reassurance that all women are being followed up appropriately.
"I understand that this may cause worry and inconvenience for the women affected and I sincerely apologise for this.
I would like to reassure everyone that the samples that were reviewed were a small percentage of those screened and reported between April 2018 and June 2018.
"The stringent quality checks that are in place have reassured us that it was only a certain number of tests within this timeframe that were required to be re-examined."
The Western Trust has advised the affected women that if they have any concerns or want further information, they should contact the Western Trust's Laboratory Department on 028 7161 1350, from 5 February to 13 February between 9:00 to 17:00 GMT.