Liquid based cytology and human papillomavirus testing in cervical cancer screening

Abstract

TECHNOLOGY NAME: Tests for the human papillomavirus (HPV) Liquid-based cytology (LBC) Disease/Condition Cervical cancer is mainly caused by the sexually transmitted human papillomavirus (HPV). Among high grade precancerous lesions, 75% to 95% test positive for HPV infection. In 2003, an estimated 1,400 women in Canada will develop invasive cervicalcancer and 420 women will die from this preventable disease. Precancerous lesions can be detected through screening and treated before they develop into invasive cervical cancer.
TECHNOLOGY DESCRIPTION: In LBC, which is a variation of conventional cytology, cells collected from the cervix are immediately preserved and spread in a monolayer on a glass slide for viewing under a microscope. The intent of the immediate fixation and the uniform spread of cells is to reduce sampling errors. Tests for HPV involve detecting and identifying the genetic material of the virus which exists as many strains.
THE ISSUE: The Pap smear is the most common screening method used to detect precancerous changes in cervical cells. Several new technologies are being evaluated to determine their ability to detect cervical cancer and its precursor stages. LBC and HPV testing may offer advantages over the Pap smear.
OBJECTIVES: 1) To evaluate the diagnostic accuracy of LBC and HPV testing to detect precancerous or malignant cervical lesions 2) To evaluate the comparative cost and cost effectiveness of LBC and HPV testing.
METHODS: The literature was searched between January 1997 and July 2003 for comparative trials that examined the diagnostic accuracy of LBC and HPV testing and Pap smears. The outcomes were estimates of test sensitivity and specificity. Economic evaluations or cost studies of LBC and HPV testing were identified through a literature search. The outcomes examined were average costs per patient, life days saved and incremental cost per life year saved relative to those for Pap smears.
CONCLUSIONS: 1) For women with an ordinary risk of cervical cancer, but not for women at high risk, LBC is more sensitive than the Pap smear; 2) LBC produces a lower rate of unusable samples of cervical cells; 3) HPV testing, alone or with cytology, is more sensitive than the Pap smear but less specific for primary screening and triage; 4) LBC screening every three years or longer may be as cost-effective relative to the Pap smear; 5) Economic modelling based on the use of LBC in a Canadian context is needed before conclusions can be made about the costeffectiveness of HPV testing.