Molecular Test Increases Specificity for Human Papillomavirus

Three different tests have been compared for the detection of human papillomavirus (HPV) on cervical specimens and correlated with the presence of cancer.

The tests are molecular diagnostic kits that either identify messenger ribonucleic acid (mRNA), or use hybrid capture DNA technology. A real-time multiplex nucleic acid sequence-based amplification assay (NASBA) for isothermal amplification and detection of mRNA was also compared.

Scientists from the Memorial University, (St. John's, NL, Canada), collaborating with others, tested cervical specimens from a random sample of 1,418 women referred for colposcopy and assessment of cervical cancer risk and 1,373 women undergoing routine screening. The three tests were the Aptima HPV assay which detects E6/E7 mRNA of 14 oncogenic types, a Hybrid Capture 2 DNA test (HC2), and an HPV Proofer assay which amplifies and detects E6/E7 mRNA from five high-risk oncogenic types. The oncogenes E6 and E7 are associated with HPV and these proteins are involved in initiation and mediation of oncogenic process that leads to cervical cancer, and to other HPV-associated cancers.

The investigators report that among 1,418 women studied, the Aptima HPV test, (Gen-Probe Inc.; San Diego, CA, USA), detected 96.3% of women with high-grade cervical intraepithelial neoplasia (CIN) or worse (CIN 2+) compared to 94.3% for the HC2, (Qiagen; Mississauga, ON, Canada). The Aptima test has far fewer false positives than HC2. Across histological grades, the Aptima assay showed significantly higher sensitivity and significantly lower specificity than the PreTect HPV-Proofer NASBA assay (Norchip; Klokkarstua, Norway), However, the Proofer test detected all eight cases of invasive cervical cancer, and this included the case which tested negative by HC2.

The authors concluded that their data indicated that the Aptima test is as sensitive as HC2, but more specific for detecting CIN 2+ and has the potential to serve as a reliable test for both primary cervical cancer screening and the triage of borderline cytological abnormalities. Samuel Ratnam, PhD, the senior author of the study, said, "Reducing false-positive result avoids unnecessary additional tests and follow-up, the associated health care costs, and distress to women. HPV infection is highly prevalent, but only a small fraction of the infected is at risk of developing HPV-associated cancers." The study was published in February 2011, in the Journal of Clinical Microbiology.

Memorial University
Gen-Probe Inc.
Qiagen
Norchip



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