The inadequacies of instruments used for cervical screening.

Cervical cytology has a high false negative rate, especially for adenocarcinoma and its precursors. This study compares the traditional spatula with the cytobrush. Both the modified Ayre spatula and the cytobrush were found to be inadequate in a significant number of patients with known cytological atypia. It is concluded that inadequate sampling instruments make a contribution to false negative rates and that brush cytology is superior to rigid instrument cytology in routine cervical screening.