The Ayre's spatula, which is widely used in the collection of samples for Pap smears, is the least effective of the major devices used for Pap smear collection, according to a review of 39 smear test trials.
The failure of such a device may be one reason why the false negative rate in pap smears can be as high as 55 per cent in some areas.
Researchers at St Mary's Hospital, Manchester examined 39 studies of various devices used for collection of cervical cells and compared their ability to identify two well known markers of cancer, endocervical cells and dyskaryosis. Their findings have produced something of a shock for proponents of regular screening.
They also show that the accuracy of a smear test is may depend entirely on which device is used.
The most effective single devices were shown to be those with an extended tip; the Ayre's spatula has a double rounded tip. The most accurate method of collection was a combination of an extended tip spatula and a small cervical brush.
The choice of device in any practice, say the authors, is usually down to habit, rather than effectiveness, and many doctors do not like using the combination of devices because it is more time consuming.
The authors recommend that, at the very least, extended tip spatulas should replace the Ayre design, and that this recommendation should be incorporated into national screening programme protocols (Lancet, 1999; 354: 1763-70).