Does liquid-based technology really improve detection of cervical neoplasia? A prospective, randomized trial comparing the ThinPrep Pap Test with the conventional Pap Test, including follow-up of HSIL cases.

OBJECTIVE: To compare the sensitivity, specificity and specimen adequacy of the ThinPrep Pap Test (TP) with the conventional Pap Test (CV) in a low-risk population with subsequent follow-up of HSIL cases. STUDY DESIGN: A prospective, randomized, controlled design was chosen to compare the TP with CV. Cytologic diagnosis and specimen adequacy were evaluated and compared with histology data in high grade squamous intraepithelial lesion (HSIL) cases. Fifteen gynecologists in private practice, all trained in colposcopy, participated in the trial. Cytologic diagnosis, specimen adequacy and follow-up of the cytologic HSIL cases were compared in the two groups. In total, 1,999 patients were included, 997 in the TP group and 1,002 in the CV group. Randomization assignments were designated on cytology case report forms, which were placed in sealed envelopes. Each envelope had a sequential randomization number on the outside to allow tracking and authentication of randomization assignments. RESULTS: Comparison of results between CVs and TPs revealed no statistically significant differences in all diagnostic categories, ranging from "within normal limits" to HSIL. Specimen adequacy, however, was superior with CVs (P < .001). The cytologic diagnosis of HSIL correlated with the histologic diagnosis in 91% of the TP group and 100% of the CV group. CONCLUSION: Because there was no statistically significant difference in sensitivity and specificity of the two techniques, improved detection of cervical abnormalities and better specimen adequacy might not be a consequence of utilizing liquid-based preparations but of a better sampling technique. Removing mucus and cellular debris from the cervical surface with a cellulose swab before sampling cells with a proper sampling device results in the same sensitivity and specimen adequacy and is much less expensive than the liquid-based technique.

Sampling, sampling errors and specimen preparation.

To obtain an adequate cervical smear for making a correct cytologic diagnosis, smear taking, laboratory handling and interpretation must be optimal. Many people are involved, and only by a combined effort of all links can this target be seriously approached: the smear takers will have to be open minded about technical improvements and read the morphologic descriptions cautiously; in the laboratory, cytotechnicians and physicians will have to challenge themselves and each other. It is mandatory to discard specimens that do not meet general standards of adequacy. At present a host of new techniques are being implemented. It is not feasible for all laboratories to be engaged in testing these new methods, but we are all requested to follow the development the best we can and switch to new ways when justified. Our working conditions are very different; therefore, it is our professional responsibility and plight to respond at the right time. So far the conclusion is that the conventional Pap smear is the international standard of care for the diagnosis of cervical cancer precursers in cancer screening programs. Certainly, this may change within a very short time. Liquid-based techniques, and in particular HPV technologies, are just around the corner.