Cancer screening uptake: association with individual characteristics, geographic distribution, and time trends in Italy

BACKGROUND

In Italy, organized screening programmes invite the vast majority of the population for cervical and breast cancer, and about one half of the population for colorectal cancer. Programme activity and quality are closely monitored. Nevertheless, there is a vast spontaneous activity, both public and private, for which information on service and coverage is missing. To estimate actual population coverage for the three types of screening the extent of spontaneous screening needs to be known.

METHODS

PASSI is a national telephone-interview surveillance system that continuously collects information about behavioural health risk factors and the diffusion of preventive health interventions. From 2010 to 2013, more than 151,000 18- to 69-year-olds were interviewed. During 2013, 136 out of 147 Italian local health authorities participated in the survey. Information about screening includes: test uptake (Pap smear, HPV, mammography, faecal occult blood test, colonoscopy), date of the last test, provider of the last test (whether paid or for free, proxy of the organized screening programme), reason for not participating in screening, and screening promotion/recommendation received. Individual information on socio-economic characteristics is available.

RESULTS

Seventy-seven percent of the 25-64 year-old women interviewed said they had undergone a Pap smear or HPV test in the three years before the interview, 40%within the screening programme, 37% spontaneously and paying. Seventy percent of the 50-69 year-old women interviewed reported having had a mammography in the two years before the interview, 51% within the screening programme, 19% spontaneously and paying. Thirty-eight percent of the 50-69 year olds interviewed reported having undergone colorectal screening in the two years before the interview, 31% within the screening programme, 7% spontaneously and paying. All three screening programmes showed a decreasing North-South trend in coverage. From 2010 to 2013, coverage increased for all types of screening; the trend was stronger in the South; the increase was mostly due to the tests performed within the organized programmes. People with low education, economic problems, and immigrants from high migration pressure countries had lower coverage levels. In regions with well-implemented organized screening programmes, test coverage was higher and differences for socio-economic factors were smaller than in regions with incomplete programme activation.

Resolving statistical uncertainty in correlation dimension estimation

In this paper we propose a novel method for obtaining standard errors and confidence intervals for the correlation dimension estimated on an observed chaotic time series. This method is based on the U-Statistics theory and an ingenious combination of the moving block and parametric bootstrap procedures. We test the method on the basis of computer simulations for both clean and noisy series. We show that the distribution of the correlation dimension estimate obtained by our method agrees very well with the "true" distribution obtained by the Monte Carlo simulation. One of the main advantage of our method is the ability to estimate the distribution (and hence, the standard error) of the correlation dimension estimate using only one observed time series.