A comparison of liquid-based cytology and Pap smear as a screening method for cervical cancer

Abstract. The implementation of population-based screening for cervical cancer with Pap smear in the early sixties was set to detect and treat precancerous lesions, hopefully preventing a subsequent invasive cervical cancer. Epidemiological data indicate that organized screening has a major impact on morbidity and mortality from cervical cancer. The limited sensitivity of a single smear necessitates repeated smears in organized program. It is suggested that liquid-based cytology improves the sensitivity. The aim of this split-sample study was to compare ThinPrep liquid-based cytology with conventional Pap smear, relying on a laboratory with long-term experience of the latter. In total, 137 women with atypical Pap smear in population-based cervical screening were enrolled for the splitsample study. The performance of both techniques (ThinPrep liquid-based cytology and conventional Pap smear) were compared and validated by a histological follow-up. Women without representative histological biopsy were excluded from the study. Pap smear had sensitivity for detection of CIN2-3 of 47% compared to 66% for liquid-based material. The concordance of the two sampling techniques with the histological diagnosis was 37% and 53%, respectively, this difference being statistically significant. The proportion of reports on atypical squamous cells of undetermined significance (ASCUS) was significantly less in the liquidbased material, 4.3% compared to 8% of the conventional smears. This improved sensitivity in combination with the possibility to perform reflex testing such as HPV DNA or p16 immunocytochemistry without renewed sampling gives ThinPrep a substantial advantage and makes the liquid-based technique interesting.

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 Comparative Analysis of Conventional Papanicolaou Tests and a Fluid-Based Thin- layer Method

● Context.—A fluid-based, direct-to-vial method of thinlayer gynecologic cytology (ThinPrep Pap Test) is reported to be more effective than the conventional Papanicolaou test in the detection of squamous intraepithelial lesions. Objective.—This retrospective analysis evaluated the validity of the findings on the thin-layer method using case material at a large independent laboratory and represented a comparison of performance of both methods over an identical period. Methods.—Data for conventional and ThinPrep tests were compared for 2 periods. Period 1 included 1 421 080 conventional and 56 835 ThinPrep specimens, and period 2 included 564 270 conventional and 109 784 ThinPrep specimens. Squamous intraepithelial lesions were used to determine detection of disease. These 2 sets of data were also analyzed to eliminate effects of any selection bias toward ThinPrep for high-risk patients. Results.—Use of ThinPrep showed a greater than 100% increase in the detection rate of squamous intraepithelial lesions (1.3%–3.4% in period 1 and 1.3%–2.9% in period 2), which was statistically significant after correcting for selection bias. We also found a significant decrease in the false-negative proportion (57% in period 1 and 35% in period 2). There was a marked improvement (233%) in the detection of high-grade squamous intraepithelial lesions in high-risk cases and a decrease in the atypical squamous cells of undetermined significance to squamous intraepithelial lesion ratio from 3.1 to 1.5 in period 2. Conclusion.—ThinPrep is better than the conventional Papanicolaou test in detecting squamous intraepithelial lesions and is a superior screening test in detection of precancerous changes of the cervix. (Arch Pathol Lab Med. 2003;127:200–204)

 

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Additional independent studies: Increased Disease Detection with the ThinPrep Pap Test

In published, peer-reviewed studies, the ThinPrep Pap Test has been proven to provide consistent, reproducible results.1-10 Independent, multi-study reviews cited consistent, increased detection with the ThinPrep Pap Test.

 

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