Objective The objective of this study was to compare the sensitivity of cervical cytology using conventional smears and SurePath liquid-based cytology (LBC).Design Prospective randomised evaluation of diagnostic test.Setting A single institution colposcopy clinic.Population Women attending first visit colposcopy appointments were offered entry into the study.Methods Cervical cytology samples from 913 women of age 16-75 years were randomly processed as SurePath LBC or conventional smears. Conventional smears were taken for 453 women and a SurePath LBC taken for 451 women. Cytology results were correlated with colposcopic findings and histology from colposcopic biopsies, treatment and follow up.Main outcome measures To compare the sensitivity of SurePath LBC and conventional smears for histologically proven abnormality.Other outcome measures include a comparison of their sensitivity for high-grade abnormalities and their satisfactory rate.Results Accounting for all randomised samples, there was a trend towards improved sensitivity for SurePath LBC (79.1 versus 73.7%, P = 0.1). However, excluding unsatisfactory cytology (and samples not taken) eliminated this trend; the sensitivity for both LBC and conventional smears for any epithelial abnormality was 81%. With a threshold of atypical squamous cells of uncertain significance (ASC-US), both SurePath LBC and conventional smears had a sensitivity of 92% for high-grade lesions. SurePath LBC was less likely to be reported as unsatisfactory (2.7 versus 9.1%, P < 0.0001).Conclusions In this context, with a threshold of ASC-US, both SurePath LBC and conventional smears offer high sensitivity for the detection of CIN2/3, but SurePath LBC is less likely to be reported as unsatisfactory.Keywords Cervical cytology, liquid-based cytology, sensitivity, SurePath.Please cite this paper as: Sykes P, Harker D, Miller A, Whitehead M, Neal H, Wells J, Peddie D. A randomised comparison of SurePath liquid-based cytology and conventional smear cytology in a colposcopy clinic setting.
It is essential not to underestimate the significance of unsatisfactory Pap results, especially in populations with extended screening intervals and/or inefficient call-back systems, as this may result in missed opportunities to diagnose significant disease and prevent cervical carcinoma. Thus, it is recommended that the clinical performance results from the study population in which unsatisfactory specimens were excluded be interpreted with caution. j Unsatisfactory cervical cytology screening specimens are associated with missed cervical dysplasia and cancer References Author's ReplySir, Thank you for the opportunity to respond to the informative letter by Dr Nance, 1 this highlights the importance of unsatisfactory smear reports in the interpretation of the clinical performance of cervical cytology tests.As stated in our manuscript, 9% of conventional smears were reported as unsatisfactory as opposed to 3% for SurePath tests. Clearly, these tests represent a missed opportunity for the detection of high-grade lesions. The clinical significance or risk of the unsatisfactory smear depends on the prevalence of high-grade abnormalities in the population, the likelihood of a repeat smear being taken and whether women are having regular smears.Despite the high unsatisfactory rate in our study and a high incidence of high-grade abnormalities, on an intention-to-treat basis, the improved sensitivity in the liquidbased arm did not reach statistical significance. Similarly, in the large randomised study reported by Ronco et al. 2despite an almost double risk of unsatisfactory reports in the conventional arm, the improvement in detection of high-grade histological abnormalities failed to reach statistical significance.In New Zealand, the incidence of an unsatisfactory smear report is about 4%. During the New Zealand Cervical Cancer Audit, 3 smear histories were reviewed. In addition, 336 smears taken in the 4 years prior to the diagnosis of cervical cancer and not reported as high grade were reread in a blinded fashion as were 3785 control smears. In this time period, all smears were conventional pap tests. There was no evidence of an excess number of smears reported as unsatisfactory in women who subsequently developed cancer. Of reread smears taken prior to the diagnosis of cancer 5% were reclassified as unsatisfactory compared with 3% of control smears. However, 21% of reread smears were upgraded to high grade, and the audit's major finding was that only 21% of women with cancer were taking part in regular cervical screening.Therefore, as Dr Nance states the unsatisfactory rate is of importance in the evaluation of a cervical cytology test, and all single studies should be interpreted with caution.
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