College of American Pathologists
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  Performance of SurePath
  liquid-based cytology





cap today

June 2005
PAP/NGC Programs Review

Mary R. Schwartz, MD

The article by Terence J. Colgan, MD, and colleagues is the first published evaluation of the performance of SurePath liquid-based cytology (SP-LBC) after large-scale implementation [Results of the implementation of liquid-based cytology-SurePath in the Ontario screening program. Cancer. (Cancer Cytopathol). 2004;102:362–367]. The study was conducted in a single cervical cancer screening program in Ontario (a generally low-risk population) with multiple laboratories participating. The adequacy and detection rates of manually screened SP-LBC were compared with the historical conventional smear group from the same laboratories during the previous year, with roughly 400,000 Pap tests in each group.

The unsatisfactory rate (0.24 percent vs. 0.58 percent) and satisfactory-but-limited-by rate (19.01 percent vs. 24.02 percent) were lower with SP-LBC than with conventional smear. The detection rate of atypical squamous cells and above (ASC+) was significantly greater for SP-LBC (4.69 percent) than for conventional smear (3.81 percent). Detection rates for LSIL (1.79 percent vs. 1.19 percent), HSIL (0.32 percent vs. 0.29 percent), and LSIL and above (2.13 percent vs. 1.50 percent) were all significantly higher for SP-LBC than for conventional smear. The latter represents a greater than 30 percent increased detection of LSIL+ by SP-LBC compared with conventional smear. There was a trend for increased detection of HSIL+ by SP-LBC (0.34 percent) compared with conventional smear (0.31 percent), but this was not statistically significant and the increase was less than the manufacturer’s claim.

Of concern is the decreased detection of carcinoma in the SP-LBC group (0.01 percent) relative to the conventional smear group (0.02 percent). The authors point out that their study has two significant, albeit unavoidable, limitations. First, this was a retrospective observational study and does not have a randomized, contemporaneous control group. Second, no histological followup is available, and thus sensitivity and specificity cannot be assessed. Nonetheless, this is an important study in the validation process of a new technology. It is the largest published study of SP-LBC to date and may provide a better reflection of the potential value of this new Pap test methodology in real life than earlier research or smaller clinical studies.

Dr. Schwartz, a member of the CAP Cytopathology Committee, is director of anatomic pathology, The Methodist Hospital, Houston.