Participation rates in the organized colorectal cancer screening program, 2015–2016
Organized colorectal cancer screening was rolled out nationwide starting in 2008. Since 2010, this program has covered all French departments, with the exception of Mayotte (which became a French department on March 31, 2011). It is coordinated at the departmental level by management bodies (a total of 89 management bodies).
In 2014, the Directorate General for Health, in its decree of September 23, 2014, approved the replacement of the guaiac test (Hemoccult® II) with an immunological test (OC-Sensor®), which is easier to use, more sensitive for detecting advanced adenomas and cancers, and offers greater reliability and reproducibility. The rollout of this test was marked by an early cutoff for invitations during the last quarter of 2014 and for reading guaiac tests as of January 31, 2015. Although the immunological test was officially available as of April 14, 2015, difficulties with kit supply and/or organizational issues led to a delay in the start of the program. In practice, the mailing of the first invitations was staggered between May and December 2015: 50% of the departments did not resume sending invitations until July 2015. These departments account for 44.3% of the total eligible population. The effective invitation period averaged 17 months per department.
The 2015–2016 participation data presented here cover both guaiac tests read at the beginning of 2015 and immunoassay tests starting April 14, 2015, thus reflecting screening activity conducted over an incomplete period. The exclusion rates and the rates of individuals with a positive test result pertain to the invitation campaign using the immunological test only.
Materials and Methods
The specifications for cancer screening programs published in the Official Journal on December 21, 2006 (Appendix to No. 295) stipulate that individuals aged 50 to 74 must be invited to undergo colorectal cancer screening every two years. The method for calculating the indicators is based on the data format guide and definitions of indicators for the evaluation of the national program (see Data Format Guide). The indicators are thus calculated over a two-year period, during which the entire population of a department is invited to participate in screening.
Calculation of the Participation Rate
The participation rate is the ratio of the number of people screened to the eligible population, i.e., the screening target population (men and women aged 50 to 74) from which those excluded from screening for medical reasons are subtracted. It is defined as:
The number of people screened—that is, men and women aged 50 to 74 who underwent a screening test during the evaluation period (here, from January 1, 2015, to December 31, 2016)—and the number of people excluded from screening for medical reasons are provided by the administrative bodies. The definition of medical exclusions is specified in the specifications (see above).
The average eligible population is obtained by calculating the arithmetic mean of the INSEE target population of people aged 50–74 for the calendar years 2015 and 2016, from which the average number of people aged 50–74 excluded from the program for medical reasons during those two calendar years (2015 and 2016) must be subtracted.
Note: For the purpose of comparing departments, the INSEE target population used to calculate participation rates is derived from population data provided by INSEE (2007–2042 projections, central scenario) calculated identically across the entire country.
Calculation of the exclusion rate
The exclusion rate is the ratio of the number of people excluded (temporarily or permanently) from the organized colorectal cancer screening program (see above) to the INSEE target screening population (men and women aged 50 to 74).
The number of excluded individuals is provided by the administrative bodies based on a variety of usable data sources: responses from invited individuals, files of colonoscopy procedures reimbursed by primary health insurance funds, files of diagnostic and therapeutic procedure codes, standardized reports of colonoscopy results and anatomopathological examinations…), but access to which varies depending on the administrative units.
As with the calculation of the participation rate, the average eligible population is obtained by calculating the arithmetic mean of the INSEE target population of individuals aged 50–74 for the calendar years 2015 and 2016, from which the average number (arithmetic mean) of individuals aged 50–74 excluded from the program for medical reasons during the two calendar years (2015 and 2016).
Calculation of the percentage of positive tests
This is the ratio of the number of people with a positive test result to the number of people with an analyzable test result, i.e., a test that could be read by the screening test reading centers.
This information is provided by the administrative units.
Age groups
A breakdown into 5-year age groups was used.
The 50–54 age group includes individuals who turned 50 during the year under review, even if they had not yet reached that age at the time of screening; the 70–74 age group includes individuals who had turned 75 at the time of screening, to account for the time lag in test completion for those invited at age 74.
Standardization of indicators
Participation rates, exclusion rates, and the rate of people with a positive test result are calculated by department, by region, and for France as a whole. They are standardized by age and sex relative to the 2009 French population (INSEE projection 2007–2042, central scenario). This standardization allows, by applying the same age and sex structure (that of the 2009 French population) to geographic units, for comparing results across these territories (departments or regions) and for studying changes over time in the various indicators examined.
Benchmarks
The European benchmark recommends a participation rate of the target population of at least 45% for the screening program to be cost-effective. This benchmark applies to all European countries that have implemented an organized screening program.
Results
Participation
Between January 1, 2015, and December 31, 2016, 18.6 million people aged 50 to 74 were invited to participate in the program. Nearly 5 million underwent a screening test (including just over 120,000 guaiac tests), representing a participation rate of 29.3% (see tables in PDF and Excel formats). Over the period from mid-April 2015 (the program’s launch date with the immunological test) to December 2016, the participation rate was 28.6% (see tables in PDF and Excel formats). These rates remain below the minimum acceptable European target of 45% participation1.
Participation, which had been declining slightly since 2010–2011, falling from 32.1% to 29.8% in 2013–2014, dropped sharply to 23.1% in 2014–2015, then increased during the 2015–2016 period, returning to a level similar to that observed before this sharp drop (Graph). The sharp decline observed is due to the interruption of organized screening activities in late 2014 and early 2015 (suspension of invitations in the last quarter of 2014 and launch of the immunological test in April 2015).
The participation figures for the 2015–2016 period must be interpreted with the understanding that the actual invitation period averaged only 17 months per department and that a significant portion of the population was invited late, and therefore had not yet had the opportunity to be screened by the end of 2016.
The participation rate is higher among women than among men (30.8% versus 27.8%, respectively; see tables in PDF and Excel formats), regardless of age group (see tables in PDF and Excel formats). It increases with age among men, from 24.8% among those aged 50–54 to 35.5% among those aged 70–74, and among women, from 26.7% among those aged 50–54 to 36.1% among those aged 70–74.
There is a regional disparity in participation rates (see Map 1, Map 2, and tables in PDF and Excel formats). Rates are particularly low (<20%) in the departments of Corsica, French Guiana, Paris, Hauts-de-Seine, and Lozère. The highest rates are found in Saône-et-Loire (44.1%) and Ille-et-Vilaine (47.0%), two departments where the antigen test is sent directly to invited individuals upon the second reminder. The other departments with rates above 40% are Haut-Rhin, Isère, Loir-et-Cher, Loire-Atlantique, and Maine-et-Loire. In total, 57 departments have a participation rate higher than the national average (29.3%). These departmental disparities can be partly explained (correlation coefficient rho=0.37) by the duration of the invitation period. Although the screening campaign using the serological test was launched in mid-April, its implementation varies greatly by department, with some having started as late as December 2015. The duration of screening using the new test ranged from 12 to 19 months depending on the department (Figure ). Therefore, spatial comparisons of participation rates for the 2015–2016 period must, even more so this year, be interpreted with caution.
Exclusion
Medical exclusions must be regularly reported and be as comprehensive as possible to ensure the quality of the program. They may be either permanent for medical reasons (personal or family history of adenomas or colorectal cancer, familial adenomatous polyposis, chronic inflammatory bowel disease, hereditary non-polyposis colorectal cancer, or Lynch syndrome), or temporary due to digestive symptoms or having undergone a colonoscopy within the past five years with normal results.
Over the 2015–2016 period, the exclusion rate was 12.3%, corresponding to nearly 2.4 million people excluded (see tables in PDF and Excel formats). It is slightly lower among men than among women (12.0% versus 12.5%, respectively). It increases significantly with age, from 5.9% among men aged 50–54 to 19.9% among men aged 70–74, and from 6.9% to 18.3% among women, respectively (see tables in PDF and Excel formats).
There are significant regional disparities in exclusion rates, ranging from less than 5% in Bouches-du-Rhône, Corsica, and French Guiana to 21.8% in Bas-Rhin (see Map 3 and tables in PDF and Excel formats). These regional disparities in medical exclusion rates are linked to how long the department has been participating in the program. The proportion of people excluded due to cancerous or precancerous lesions or who, following a positive test, have had a normal colonoscopy within the past five years is higher in regions that began organizing screening earlier. These regional disparities also highlight the inconsistencies in the quality of data collection across departments. The number of excluded individuals remains poorly documented in certain departments, particularly due to the poor performance of their systems for collecting data on medical exclusions. At the departmental level, there is a variety of usable data sources to document medical exclusions, but these are not always accessible to administrative bodies. This situation highlights the urgent need to optimize the collection of information on medical exclusions to ensure the quality of the program, by defining a national strategy to better guide and support the professionals involved.
Positive Tests
During the period from April 14, 2015, to December 31, 2016—the period corresponding to the invitation campaign for the serological test—4.8 million people were tested, of whom nearly 217,000 tested positive, representing a positivity rate of 4.6%. This rate is higher among men than among women (5.7% versus 3.6%, respectively), and increases with age (see Graph and tables in PDF and Excel formats).
There is significant variability in the rate of positive tests across departments, with values ranging from 3.9% in Aveyron, Savoie, Lozère, and Guadeloupe to 5.5% in Hérault (see map and tables in PDF and Excel formats).
Conclusion
Between 2015 and 2016, nearly 2.4 million people aged 50 to 74 were excluded from the program, and 5 million underwent a screening test (including just over 120,000 guaiac tests), representing a participation rate of 29.3%. For the period during which the immunological test was used (an average of 17 months per department), the participation rate was 28.6% and the positive test rate was 4.6%, in line with expectations. Participation rates must, once again this year, be interpreted with caution in the context of a period marked by the interruption of screening activities in 2014 and 2015 and by a gradual resumption and ramp-up of invitations that varied by department. Despite a several-month halt in screening activities due to the change in testing method, screening uptake remained stable. The next participation data will cover the 2016–2017 period, i.e., a period of routine screening organization, and should allow for a better assessment of the potential impact of the test change on participation.
