In the present study, we assessed the coverage determinants of screening inside and outside the BCSP in Flanders. A median 48.4% of women aged 50–69 are screened by the BCSP which is significantly higher than the 14.1% of women screened outside the program. Working women in younger age group (50–54 years of age), and women living in crowded households with low dental care go less frequently to the screening, and if they go, they tend to be screened more frequently outside the context of the BCSP.
The total median coverage rate of 60.90% of screening inside and outside the BCSP is within the range of coverage levels of European countries (average: 48.2% (range: 19.4–88.9%)) [27]. The median coverage rate of the BCSP in Flanders of 48.4% is close to the coverage rate of the BCSP in countries such as France (52.8%) [6] and Switzerland (46.7%) [7, 27] and higher than in Serbia (38.0%) [28]. In these three countries there is screening in and outside the context of the BCSP. However, it is much lower than the coverage rate of the BCSP in some western and northern European countries like the United Kingdom (78.0%), the Netherlands (78.5%), and Norway (72.1%) [27] where only the BCSP is endorsed as the population screening strategy.
From 2006 to 2016, the coverage rate of BCSP increased while the coverage rate outside the BCSP decreased. This effect might be explained by public health campaigns via mass media and community education programs [24, 29], which increased the visibility and awareness of BCSP for the target population and their doctors [29, 30]. A decrease in screening coverage rate was observed from 17.50 to 11.40% for the individuals from age 50–54 to 65–69 years old in the screening outside the BCSP, whereas this pattern was not observed for the individuals in the BCSP. A similar pattern is also observed in countries like France [6, 31] and the United States of America [32] where both screening strategies are provided in large scale. A potential explanation can be that older women are more likely to attend the relatively fixed time and place of the BCSP than younger working women.
We found that living in crowded households, living in an area with high population density, and having a low dental care are associated with a lower probability of being screened. These three characteristics are all indicators for a low SES. People living in areas with a high population density tend to have a lower SES [33]. People living in crowded household are more likely to fall into income poverty [34]. As dental care is not fully covered by the health insurance system in Flanders [35], a low dental care indicates a lower SES [36]. Similar associations are also available in the literature regarding the increased BCSP coverage and increased dental care [19], less crowded household condition [14], and decreased population density [37].
Interestingly, women that are characterized by living in an area with high population density, living in a more crowded households, or having a low dental care tend to go more frequently for screening outside the BCSP. The reverse SES gradient in the use of screening in and outside BCSP was also seen in other settings where both screening strategies coexist [6, 7, 37]. An explanation for this phenomenon is that women with a higher SES are more likely to have a higher level of health literacy [38]. For these women, information regarding the importance of mammography screening and the systematic quality control is more likely to motivate them to participate in the BCSP [5] [29]. Another explanation is that poor employed women could have less flexible working time, which can conflict with the fixed working time of organized screening units [6, 7, 37, 39]. It has also been mentioned that areas with a higher population density have a lower population BC screening capacity (defined as the number of mammography facilities per 10,000 women) [40] and that in these areas there are more private clinics for opportunistic screening [37]. As a lower capacity of screening units can induce a longer waiting time and therefore a lower satisfaction of screening experience [5], low SES women living in these areas might be more likely to have negative screening experience and as a consequence prefer to go for screening outside the BCSP [22].
The strength of this study is that we examined determinants of coverage rate of screening in and outside the BCSP with longitudinal administrative data instead of self-reported screening uptake, which may induce recall bias. For that, regular collected and maintained administrative data of screening coverage outside the BCSP were applied. This enabled us to evaluate the determinants of the two coexisting screening strategies for BC and to better understand which further efforts are needed to improve the coverage of the BCSP in Flanders. However, our study had some limitations as well. First, a limitation of this study was the use of aggregated data, which reduced the options to evaluate correlation structures in the data [41]. Similarly, due to the aggregated data, a variation of coverage rate and the associated determinants within a municipality can be concealed. However, the association between the determinants and screening uptake in our study is consistent with other studies that applied neighborhood or individual level factors [13, 18, 19]. Second, proxy variables for SES were applied instead of income which can directly characterize SES of women. However, the proxy variables used are commonly applied and the magnitude and direction of the association between variables is consistent with the literature [6, 14, 18].