Author: Tse, Sheung-shun Samson
Title: Potential for cross-contamination in the use of ThinPrep for HPV DNA detection by Digene's Hybrid Capture 2 assay : a pilot study
Degree: M.Sc.
Year: 2007
Subject: Hong Kong Polytechnic University -- Dissertations.
Cervix uteri -- Cancer -- Cytodiagnosis.
Papillomaviruses -- Testing -- Environmental aspects.
Department: Department of Health Technology and Informatics
Pages: xi, 95 leaves : ill. (some col.) ; 30 cm.
Language: English
Abstract: Cervical carcinoma is the second most common malignancy among women and the third most common cause of cancer deaths worldwide. Extensive data has indicated human papillomavirus (HPV) infection is the most important risk factor for cervical cancer. Over the years, the conventional Papanicolaou (Pap) test has been considered as the "gold standard" methodology for the preparation of cervical smears. However, it is gradually being replaced by liquid-based thin-layer cytology due to its higher sensitivity and its potential use for molecular testing such as HPV. One of the more popular liquid-based technologies in commercial use nowadays is Cytyc Corporation's ThinPrep Pap test. However, just as the combination of cytology analysis and Digene Corporation's Hybrid Capture 2 HPV DNA test (HC2) is gaining wide recognition as a primary cervical screening method, concerns have been raised over possible cross-contamination in ThinPrep 's PreservCyt transport medium and the point of controversy centres on the treatment of the filter cap in the sample preparation procedures. This study was conducted to examine the potential for cross-contamination in using ThinPrep for HPV DNA detection by HC2, by comparing the HPV DNA test results from the pre-processing materials of ThinPrep 's cervical specimens and those from their corresponding residual materials. In the initial study, the filter cap was wiped with a tissue after each specimen was processed, as recommended by Cytyc. In the follow-up study, the treatment of the filter cap remained the same after the results from the initial study did not indicate cross-contamination in the residual materials from a statistical perspective. In this study, 240 cervical samples from 120 cases were collected. In the initial study, 30 cervical cases reported as "atypical squamous cells" (ASC)/"atypical glandular cells" (AGC) and above, their immediate subsequent specimens regardless of their cytologic diagnostic categories (N = 30) and 20 end-of-day cases without regard to their cytologic diagnostic categories were collected. In the follow-up study, 40 cytologically "negative" cases that appeared immediately after cases reported as ASC/AGC and above were collected. The study showed that of the 120 pairs of the pre-processing materials and their respective residual materials of the cervical specimens, one pair reported discrepancy in their HPV DNA test results, with the pre-processing materials tested negative for HPV and the residual materials tested positive. Although this mismatch case did not bring about a statistically significant difference in the comparison between the HPV DNA test results of the preprocessing materials and those of the residual materials, meaning the potential for cross-contamination in ThinPrep's sample preparation procedures was minimal, an error rate of 0.83% (1 out of 120 cases) could put hundreds of thousands of cervical cases prepared by ThinPrep in a high-risk population setting worldwide every year at risk of being contaminated and hence delivering inaccurate HPV DNA test results. Given the potentially far-reaching impact of this 0.83% error rate, further studies should be conducted on the ideal sample preparation procedures of ThinPrep and the design of the processor to eliminate the risk of cross-contamination before it is too late.
Rights: All rights reserved
Access: restricted access

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