Dorothy L. Rosenthal, M.D., Susan Geddes, CT(ASCP), Cornelia Trimble, M.D., Kathryn Carson and Patricia M. Alli, M.D.
The Johns Hopkins Medical Institutions, Baltimore, Maryland

Introduction/Purpose:  Gynecologic cytology is utilized to screen for cervical cancer.  The Pap smear is the industry standard, but the liquid based Pap (LBP) test is fast replacing it.   Despite the success of the LBP in decreasing indeterminate results and increasing detection of neoplastic lesions, the increased cost is difficult to justify.  This study was designed to optimize a liquid based Pap test utilizing common cytopathology laboratory equipment, resulting in an inexpensive test, at least diagnostically equivalent to the conventional Pap smear.

Material and Methods:  Adult women (482) were enrolled and included in the study that had received IRB approval.  After making the conventional Pap smear slide, clinicians placed the collection device with residual cells from the uterine cervix in a preservative fluid.  The cell suspension was then received in the cytopathology laboratory, vortexed to remove cells from the collection device, and a 2 ml aliquot was diluted by an equal amount of preservative fluid.  The ThermoShandon (Pittsburgh PA) Cytospin™ device was used to centrifugally deposit the cells from the liquid onto a 20 X 10 mm area on a standard glass microscope slide.

Results:  The sensitivity and specificity for LSIL and HSIL did not significantly differ between the two methods.   Also, there were no false negatives for either method, and fewer false positives for the PapSpin method.  There was a difference in the sensitivity for a Negative interpretation, with the PapSpin having a greater proportion of true negatives.  Kappa statistic comparing agreement of the two Pap tests equaled 0.70, (P < 0.0001), a level of concordance in the “very good” category.  Quality indictors were better in the PapSpin group, except for inadequate endocervical component, which was higher in PapSpin samples, explained by the split-sample study design, which favors the conventional smear.

Conclusions:  The PapSpin is a legitimate alternative to the conventional Pap smear for the detection of cervical intraepithelial neoplasia, resulting in better preservation and improved cell visualization.  In addition, the liquid residual allows for reflex HPV-DNA or PCR testing.  Finally, the equipment costs are considerably less than the two FDA approved liquid processing methods, allowing small to moderate volume laboratories to offer this capability to their clients, and remain competitive.