Women whose cervical smears turn up mild abnormalities should not have invasive investigations, according to guidelines recently drawn up by a workshop in Oxford.

In its recommendations, called the NHS Cervical Screening Programme, the National Co-ordinating Network concluded that women with minor cell abnormalities, such as "borderline or mildly dyskarotic smears", should follow a path of "surveillence". This entails having a repeat smear six months later, only followed by a colposcopy (a visual examination of the cervix through a special instrument) if the smear continues to show abnormality.

It is recommended that women with moderate or severe abnormality be given immediate colposcopy.

These guidelines represent a complete reversal of those of 1987, which recommended that all women with abnormalities of any type be immediately given colposcopy.

The decision is based in part on two admissions, according to Joseph Jordan, a consultant at the Department of Gynaecology, Birminham and Midland Hospital for Women.

The first is that medicine doesn't understand whether "women with mild cytological abnormalities develop invasive cancer without progressing through more severe degrees of . . .abnormality."

The second, according to a BMJ study in 1988 (297:18-21), is that "nearly half of all smears with mild abnormalities revert to normal within two years, with no patient developing invasive cancer on longer term follow up."