Discussion
This study found a large and statistically significant effect of the Colonav Patient Navigation Program on deprived populations’ participation rate in CRC screening. This effect was estimated as an increase of 23% in participation in the population receiving the intervention. In addition, this study explored more broadly the interaction between the context and the intervention deployment.The quantitative context analysis highlights the differences among the districts at the beginning of the study. Initial participation rates ranged from 30 to 0%. Even with such different contexts at the beginning of the intervention, the study underlines a positive (but not significant) effect of each of the navigators. The context analysis underlined that main contextual factors identified as impacting the navigators’ mode of operation were: poverty (a major barrier to keeping healthy), language barrier (categorised as present or not) and behavior of the institutions supposed to give the navigators legitimacy (supportive or opposed). In this, our study confirms Ficella's postulate on the PN, which implies a double recognition: that of peers but also that of Institution. On the other hand, the COLONAV study broadens the description of the mechanism implemented by navigation: It highlights that the low socio-economic level of certain populations, particularly in urban districts, was a ubiquitous feature, and shaped a part of the navigators’ mode of operation: here they had to spend much time in first resolving the social problems of individuals, before starting to accompany residents to CRC screening. But this problem-solving aspect was a mandatory step towards success in their action. Depending on their previous knowledge of the population (same culture, same place of residence, same language) navigators had different levels of facilities for approaching them, and also had different intrinsic abilities. So they developed different strategies to reach people, each with its own strengths and weaknesses. The common feature was that they all relied on the existing social network and that they had to adapt and be flexible to fit with their unpredictable and moving environment. The essence of Navigation is here to make do with what is already there. It does not establish a position of its own but is a link between the already existing systems.Our results are consistent with the broad range of other published PN studies. effect of PN for CRC screening in USA has been estimated at OR = 2.01 IC95% (1.64–2.26) [The Cluster randomized design is another strength of this study, since it is adapted to population-based research, allowing it to avoid contamination bias. Another strength is the size of this study: 24,281 individuals were included, across 5 different French districts. The study included 4 different research teams from 5 disciplines. With such a large scale, the study succeeded in finding significant proof of the effectiveness of a French Patient Navigation Intervention for CRC screening among a deprived population.The study also had limitations. The first was the unfortunate timing of the course of the study, which was conducted at the same time as France changed the type of test for CRC screening from FOBT to Fecal Immunochemical Test (FIT). We had to face, in the middle of the study, a period where no tests of any kind were available. This explains the drop in participation rate between the before and the after comparison. Fortunately, the existence of control groups mitigated this effect in the results. And the effect of PN in those worst conditions remained positive, which increases the possibility of a greater effect under better conditions. The second limitation was the impossibility of having access to individual data for the target population. However, we believe that Population Health Intervention Research is by its essence ecological research. Qualitative analyses provide necessary and complementary information which is lacking in quantitative findings.