Performance of a fluid-based, thin-layer papanicolaou smear method in the clinical setting of an independent laboratory and an outpatient screening population in New England.

BACKGROUND: A patented, fluid-based, thin-layer method for preparation of Papanicolaou (Pap) smears (ThinPrep Pap test) has been reported to be significantly more effective than the conventional smear invented by George Papanicolaou. We tested this position by comparing the cytologic diagnosis and specimen adequacy results obtained using the ThinPrep method with data from conventional Pap smears obtained from a similar population.
METHODS: Test results of 56 339 ThinPrep specimens were compared with results from 74 756 conventional smear cases obtained from the same sources in a corresponding period of the previous year.
RESULTS: The use of ThinPrep for cervicovaginal cytology produced a 75.14% increase in the detection of low-grade squamous intraepithelial lesions and higher diagnoses. Detection of low-grade squamous intraepithelial lesions increased by 71.65% (from 1.58% to 2.71%), and detection of high-grade squamous intraepithelial lesions increased by 102.54% (from 0.26% to 0.52%). There was a 39.11% decrease in the atypical squamous cells of undetermined significance-intraepithelial lesion ratio (from 2.07 to 1.26). There were also marked decreases in the number of specimens categorized as "satisfactory but limited," owing to obscuring inflammation (-94.34%), obscuring blood (-99.84%), and poor fixation (-99.25%).
CONCLUSION: ThinPrep produced increased detection of premalignant precursors while improving specimen adequacy.