The human papillomavirus test (HPV) test could improve the (costÀ) effectiveness of cervical screening by selecting women with a very low risk for cervical cancer during a long period. An analysis of a longitudinal study suggests that women with a negative Pap smear and a negative HPV test have a strongly reduced risk of developing cervical abnormalities in the years following the test, and that HPV testing lengthens the detectable stage by 2 -5 years, compared to Pap smear detection alone. One of the possible uses of the human papillomavirus test (HPV) is in primary cervical cancer screening in addition to or instead of the current Pap smear (Cuzick et al, 1999a;Cuzick, 2000;Meijer and Walboomers, 2000).Introduction of HPV screening should be based on established (cost-) effectiveness. The (cost-) effectiveness of HPV testing is primarily determined by the duration of the detectable preclinical stage (the period from the HPV infection to clinical disease), and the sensitivity and costs of HPV testing. To estimate preclinical duration and sensitivity, longitudinal studies on the association between HPV infection and the development of neoplasias are necessary. Several large longitudinal screening studies have started, but no longterm results have been reported yet, although smaller longitudinal studies have been published (Rozendaal et al, 1996(Rozendaal et al, , 2000Ho et al, 1998;Liaw et al, 1999). These studies differ with respect to HPV test used, age range of women, study design, and cytological or histological endpoint, which complicates the comparison and interpretation of these results. It is therefore too early for definite answers on the value of HPV testing in primary screening (Myers et al, 2000;Kim et al, 2002;Mandelblatt et al, 2002). However, available data can be explored to derive preliminary estimates for parameters that determine the cost-effectiveness of HPV testing. This study investigates the duration of the detectable preclinical stage using the results of Rozendaal et al (2000). For these estimates, the 5-year cumulative incidence of cervical intraepithelial neoplasia (CIN) III after a negative Pap smear, the current screening interval in the Netherlands, is compared with the cumulative incidence within a doubled screening interval of 10 years (Meijer and Walboomers, 2000) in case of a negative Pap smear and a negative HPV test.
MATERIAL AND METHODSThe study population, and screening and follow-up results are described in Rozendaal et al (1996Rozendaal et al ( , 2000. Briefly, the smears obtained during routine screening from 1988 to 1991, from a cohort of 2250 women aged 34 -54 years, who were either normal or who showed borderline nuclear changes were tested for a highrisk HPV. The women were followed during a mean period of 6.4 years, using screen-detected (histologically confirmed) CIN III as end point. Among the 2129 (95%) women with a negative HPV test at baseline, one case of CIN III was diagnosed at a following screening round. Of the 121 women with a positive HPV test result at b...