Accuracy of cervical smears in predicting the grades of cervical intraepithelial neoplasia

This is a retrospective study carried out to assess the correlation between the cytology and histology of cervical intraepithelial neoplasia in 1325 women. A poor correlation between the cytologic and histologic diagnosis of the various grades of CIN was shown. Forty-one percent of smears with repeated borderline change and 50% of those predicting CIN1 showed a higher grade of CIN on histology. The overall apparent false negative rate of cervical smears for high grade CIN (CIN2 and CIN3) was 19% and for CIN3 alone was only 3%. It is therefore concluded that there is a consistent tendency for cervical cytology to underestimate the severity of histologic lesions and it is therefore important that the clinicians ensure adequate follow-up of patients whose smears show a lesser degree of abnormality.