REPEAT smear tests are being recommended for 369 women whose samples - taken during July-October last year - were sent for screening in out of date sample pots.

Screening body Cervical Screening Wales has written to the women to advise them of the issue.

Smear tests are carried out at GP practices, sexual health clinics and hospital clinics, with the cervical sample being put into a vial containing preservative fluid. It is then returned to the Cervical Screening Wales laboratory for screening.

It has been found that, for a very small percentage of samples, vials past the manufacturer’s expiry date were accidentally used, during this period last year.

Some affected samples were screened before the issue was identified, and Cervical Screening Wales has been working to review test results and to contact the women affected, to offer advice.

The issue affects fewer than two per cent of women who received cervical screening in Wales during last July-October.

“We apologise sincerely to all women who will receive a letter from us related to this issue," said Dr Sharon Hillier, director of screening for Public Health Wales.

“I can reassure women that there is no evidence that any harm has been caused by this issue. We have looked carefully at all of the results issued already and where possible have rescreened samples.

“Anyone who has not received a letter from us has not been identified as affected by the issue, and does not need to be concerned or to contact us.

“We continue to work with our health board partners to investigate how this issue arose and ensure appropriate procedures are in place.”

The incident took place at a time when Cervical Screening Wales was rolling out HPV screening - testing for the virus that causes nearly all cases of cervical cancer.

Just under half of the affected women were screened for HPV and will be advised that they should arrange a repeat smear test, as their sample cannot be rescreened.

The remaining samples, those which were initially examined for abnormal cells, have been rescreened. Of the affected women, the majority will be advised that their result is unchanged and they do not need to take further action.

A very small number - fewer than three per cent of those whose samples were rescreened - will be advised that they should have a repeat smear test.

Women in Wales aged 25-49 are invited for a smear test every three years, and women aged 50-64 are invited every five years.

More information on Cervical Screening Wales is available at: www.cervicalcscreeningwales.wales.nhs.uk