Video monitoring of smear‐taking at colposcopy: relationship to cytology

Objective  To investigate the reasons why cervical smears occasionally fail to reflect the underlying pathology in the cervix even when the smear is taken at colposcopy. Design  A randomised study of three different smear-taking devices. Setting  A colposcopy clinic. Population  Women attending the colposcopy clinic. Methods  A smear was taken from 172 nulliparous and 100 multiparous women at colposcopy and the procedure was monitored on a video-imaging system. The cytological findings were compared with the biopsy report in 147 nulliparous and 85 multiparous women. Main outcome measures  Accuracy of cytology and the effect of a range of variables on the accuracy of cytology. Results  Sampling of the transformation zone was incomplete in 15% of nulliparous women and 8% of multiparous women. Univariate analysis of a range of variables including parity, type of sampling devices, completeness of sampling of the transformation zone, size of the transformation zone, size of the lesion (aceto-white area) and location of the squamo-columnar junction showed that the accuracy of cytology was influenced by all these factors except for parity and smear-taking devices. Multivariate analysis showed that the location of the squamo-columnar junction, the size of the transformation zone area, the size of the aceto-white area and the ratio of the aceto-white area to the area of the transformation zone influenced the accuracy of cytology. Conclusions  Women with large transformation zone areas (>30.03 mm2) and/or small aceto-white lesions (<7.01 mm2) are more likely to have an inaccurate cytology reports than women with small transformation zone and women with larger aceto-white areas. A ratio of the aceto-white area to the area of the transformation zone of 0.22 or less increases the risk of disagreement between the cytological and histological findings.