Background: The authors noted a significant increase in the diagnosis of atypical squamous cells of undetermined significance (ASCUS) in premenopausal women using oral contraceptive pills (OCP) (9%) versus women not on OCP (4%) using ThinPrep Pap smears (P = 0.02). The purpose of this study was to correlate these morphologic changes with human papillomavirus (HPV) DNA detection by in situ hybridization and clinical follow-up.
Methods: Eighty-four ThinPrep Pap smears diagnosed as ASCUS or ASCUS favor low-grade squamous intraepithelial lesions (LGSIL) in young women receiving OCP were studied by HPV in situ hybridization. This information was correlated with colposcopic follow-up and AutoCyte Pap smear results. The authors also studied 80 ThinPreps from young women with a Pap smear diagnosis of unequivocal LGSIL where there was a corresponding biopsy (positive controls) and 40 ThinPreps diagnosed as within normal limits and that rescreened as such (negative controls).
Results: The detection rate of HPV DNA by in situ hybridization was 33% (28 of 84) in ASCUS cases versus 90% (72 of 80) for cases of unequivocal LGSIL. A blinded review of the 29 ASCUS Pap smears performed by AutoCyte showed that 66% (19 of 29) were diagnosed as within normal limits. The majority of the cervical biopsies in the women with ASCUS by ThinPrep Pap smears were negative for dysplasia (29 of 39 [74%]) whereas 71 of 80 biopsies (88%) showed dysplasia in women with Pap smears diagnosed as unequivocal LGSIL. The periodic acid-Schiff (PAS) stain demonstrated that many of the cells with halos in the ThinPrep Pap smears that mimicked LGSIL contained glycogen.
Conclusion: The ThinPrep induces changes that mimic LGSIL in young women on OCP. These artifacts may reflect pressure-induced alteration of glycogen. PAS analysis and, more directly, HPV testing by in situ hybridization can help differentiate this mimicking from actual LGSILs.
Copyright 2003 American Cancer Society.