Although cervical cancer screening has been available for more than 20 years, about 12,800 new cases were diagnosed and 4,500 related deaths occurred in the United States in the year 2000. Screening can reduce mortality rates by 46 percent, but advanced cases still occur because of false-negative screening test results. New screening techniques that involve liquid-based cytology (LBC) and testing for human papillomavirus (HPV) offer more sensitive screening that may allow for a longer interval between tests. Maxwell and colleagues analyzed the costs and outcomes of new screening methods for cervical cancer to determine the optimal type and interval of screening tests for use in large populations of healthy women.
They developed a Markov model, based on the natural history of HPV infection and the etiology of cervical cancer, and applied the model to a theoretic cohort of 100,000 healthy women beginning at 18 years of age and lasting until 85 years. In this cohort, the model was used to predict the cervical cancer mortality and costs associated with three methods of screening (i.e., conventional Papanicolaou [Pap] screening, LBC screening alone, and LBC plus HPV). For each technique, they estimated the implications of screening every year and compared this with screening at two- and three-year intervals.
With no available screening, an estimated 1,001 deaths attributable to cervical cancer would occur in the cohort population. Even the simplest option, conventional Pap screening every three years, reduced this rate to 189 deaths. Pap screening at two- and one-year intervals was estimated to result in 116 and 40 deaths, respectively (see the accompanying table).
The cost-effectiveness of the different strategies depended on the screening interval. As the test sensitivity rises, the specificity tends to decrease, resulting in more costs to manage false-positive results. Both conventional Pap smears and LBC become cost-effective when performed every three years. When all associated follow-up and treatment costs are taken into consideration, LBC plus HPV screening every three years costs less than $50,000 per year of life saved.
The authors conclude that the most sensitive cervical screening tests, LBC or LBC plus HPV testing, are cost-effective when performed at three-year intervals but not when performed annually.