Models of screening

This article describes models for disease screening and how they have developed in recent years. The discussion focuses on screening for cancer, because most of the methodological advances in screening design and evaluation have concerned cancer screening. The first part of the article describes the characteristics of these models and illustrates them with a discussion of a simple screening model. The second part describes the development, strengths, and weaknesses of the two main types of screening model—analytic and simulation models—with a particular focus on microsimulation models. The third part discusses model fitting and validation, and the final part briefly describes models for diseases other than cancer—in particular, models for screening for infectious diseases—and discusses the current state and possible future directions for models of disease screening.

The Australian bowel cancer screening pilot program : analysis of routinely collected screening data

This report presents analyses of monitoring data from the Australian Bowel Cancer Screening Pilot Program. The purpose of the analyses is to support the overall evaluation of the Pilot and to inform the planning of the proposed national bowel cancer screening program.

Cervical screening in Australia 2002–2003

The report presents most recent information on participation in cervical screening, rate of early re-screening, low-grade and high-grade abnormalities detected, incidence of cervical cancer and mortality. Analyses of incidence and mortality data by location (major cities, regional and remote) as well as mortality by Indigenous status are also presented. Where possible, data are presented by state and territory stratification.

Cervical screening in Australia 2001–2002

This report is the sixth national report on the performance of the National Cervical Screening Program in Australia. Cervical screening services are provided as part of mainstream health services with general practitioners performing approximately 80% of Pap smears. The program is funded by the Australian Government, and the state and territory governments.

This report presents statistics on the performance monitoring indicators agreed to by the National Advisory Committee to the program.

Cervical screening in Australia 2000–2001 and 1999–2000

This is the third annual report based on key program activity, performance and outcome indicators to monitor the achievements of the National Cervical Screening Program. The report provides a comprehensive national picture of cervical screening in Australia for 2000-2001 and 1999-2000. The report presents most recent information on participation in cervical screening, rate of early rescreening, low-grade and high-grade abnormalities detected, incidence of cervical cancer and mortality. Analysis of incidence and mortality data by location (rural, remote and metropolitan) as well as mortality by Indigenous status are also presented. Where possible, data are presented by state and territory stratification.

Cervical screening in Australia 1999–2000

Cervical Screening in Australia 1999-2000 provides a comprehensive national picture of cervical screening in Australia for the two-year period 1999-2000, based on key program activity, performance and outcome indicators.The report presents the most recent information on participation in cervical screening, the rates of early re-screening, detection of low-grade and high-grade abnormalities, and cervical cancer incidence and mortality. It includes analyses of incidence and mortality by location (rural, remote and metropolitan) as well as mortality by Indigenous status. Where possible, data are presented by State and Territory as well as for Australia as a whole. Cervical Screening in Australia 1999-2000 is the fourth annual report of the National Cervical Screening Program

Cervical screening in Australia 1998–1999

This report provides a comprehensive national picture of cervical screening in Australia for 1998-1999. It presents most recent information on participation in cervical screening, rate of early re-screening, low-grade and high-grade abnormalities detected, incidence of cervical cancer and mortality. Analysis of incidence and mortality data by location (rural, remote and metropolitan) as well as mortality by Indigenous status are also presented.

Adjuvant therapy, not mammographic screening, accounts for most of the observed breast cancer specific mortality reductions in Australian women since the national screening program began in 1991

There has been a 28% reduction in age-standardised breast cancer mortality in Australia since 1991 when the free national mammographic program (BreastScreen) began. Therefore, a comparative study between BreastScreen participation and breast cancer age specific mortality trends in Australia was undertaken for two time periods between 1991 and 2007, where women aged 50–59 and 60–69 years, who were invited to screen, were compared to women aged 40–49 and 70–79 years who were not invited, but who did have access to the program. There were mortality reductions in all four age groups between 1991–1992 and 2007, resulting in 5,849 (95% CI 4,979 to 6,718) fewer women dying of breast cancer than would have otherwise been the case. Women aged 40–49 years, who had the lowest BreastScreen participation (approximately 20%), had the largest mortality reduction: 44% (95% CI 34.8–51.2). Women aged 60–69 years, who had the highest BreastScreen participation (approximately 60%), had the smallest mortality reduction: 19% (95% CI 10.5–26.9). As BreastScreen participation by invited women aged 50–69 years only reached a maximum of about 55–60% in 1998–1999, a decline in mortality in Australian women cannot be attributed to BreastScreen prior to this time. Thus, almost 60% of the Australian decline in breast cancer mortality since 1991 cannot be attributed to BreastScreen. Therefore, mammographic screening cannot account for most of the reductions in breast cancer mortality that have occurred in Australian women since 1991 and may have contributed to over-diagnosis. Most, if not all, of the reductions can be attributed to the adjuvant hormonal and chemotherapy, which Australian women have increasingly received since 1986.

Statistical models for cancer screening

This paper reviews the application of statistical models to planning and evaluating cancer screening programmes. Models used to analyse screening strategies can be classified as either surface models, which consider only those events which can be directly observed such as disease incidence, prevalence or mortality, or deep models, which incorporate hypotheses about the disease process that generates the observed events. This paper focuses on the latter type. These can be further classified as analytic models, which use a model of the disease to derive direct estimates of characteristics of the screening procedure and its consequent benefits, and simulation models, which use the disease model to simulate the course of the disease in a hypothetical population with and without screening and derive measures of the benefit of screening from the simulation outcomes. The main approaches to each type of model are described and an overview given of their historical development and strengths and weaknesses. A brief review of fitting and validating such models is given and finally a discussion of the current state of, and likely future trends in, cancer screening models is presented.

Cost-effectiveness of mammographic screening in Australia

The purpose of this research was to estimate the cost-effectiveness of mammographic screening to supplement the results of the National Evaluation of Breast Cancer Screening which identified the mortality benefit as the most sensitive parameter. This appraisal used a different computer model, MISCAN, which models the effects of introducing a national screening program into a previously unscreened population, rather than basing estimates on the assumption of a fully established program. For the 40 to 49 age group a mortality reduction of 8 per cent was assumed, rather than the 30 per cent estimate utilised in the National Evaluation. The revised estimate is based on the two Swedish trials (Malmo and WE). New estimates for treatment costs were also incorporated into the MISCAN model. The cost-effectiveness of the policy recommended in the National Evaluation Report, $11 000 per life year saved with two-yearly screening of women over 40, is estimated by the MISCAN model to be $20 300. These differences arise partly from the difference in mortality effects for the 40 to 49 age group, but also from differences inherent in the steady-state and dynamic population approaches to modelling premature deaths averted. The MISCAN results confirm that screening for women over 50 is more cost-effective than screening women under 50. Screening all women aged 50 to 69 every two to three years is reasonable value for money. For women aged 40 to 49 the mortality benefit and cost-effectiveness is less clear, and it would be prudent to allow screening in this group until further evidence is available.