Colorectal screening and diagnostic procedures at present generally must be performed by a specialized physician. Our study was able to identify a target for the number of gastroenterologists to improve the uptake of colorectal endoscopy exams. We found that at least three gastroenterologists per 100,000 people could yield significantly higher colorectal exam rates.
Our finding that the supply of gastroenterologists can positively influence the overall rate of colorectal endoscopy screening is consistent with prior work. There appears to be growing evidence that increasing the supply of professionals qualified to conduct colonoscopies is a modifiable factor that can improve colorectal cancer screening.34–37
We also found that the health insurance market was important in shaping endoscopy screening for colorectal cancer. Areas characterized by high levels of uninsurance are unlikely to be attractive locations for screening and diagnostic services because facilities need a relatively large number of patients to recover costs.32,33
By extension, it is possible that the negative impact of uninsurance could extend to everyone in the community, regardless of individual health insurance status.33
Thus, health insurance seems to be related to colorectal cancer screening by increasing the likelihood that a local community will be able to sustain an appropriate level of colorectal cancer screening facilities. Therefore, the health insurance market of a community may be a modifiable factor to use in focusing public policy efforts on improving colorectal cancer screening, and perhaps other forms of preventive screening for the general population.
Our study also attempted to explain racial and ethnic disparities in colorectal endoscopy use. We discovered that various factors, including access to care as measured by individual-level health insurance coverage, access to a usual source of care, and transportation barriers, along with county-level indicators of access such as the supply of gastroenterologists and the health insurance market, were unable to fully explain disparities. This finding is also consistent with conclusions from recent studies.12–15,28–36
Specifically, our finding that the supply of gastroenterologists was unable to substantially explain racial and ethnic disparities was similar to conclusions reached in prior research studies.35,36
However, a recent study using Texas Medicare claims data found that increased supply of colonoscopists and primary care physicians was associated with higher screening colonoscopy uptake among whites and lower uptake among racial and ethnic minorities.37
The strength of this study, compared to other studies, was its ability to clearly differentiate screening colonoscopies versus colonoscopies for diagnostic purposes and other colorectal screening and diagnostic modalities. However, the study population was restricted to people age sixty-five or older living in Texas, which is not generalizable to the population group that is recommended for screening (people age fifty or older, or people age forty or older with a family history of colorectal cancer).
Therefore, there is still a need for analysis of generalizable data on the recommended screening population using measures that can differentiate colonoscopies for screening versus diagnostic purposes.
Despite our ability to measure and account for numerous factors that may influence the likelihood of undergoing a colorectal exam, we found persistent disparities that need further research. The only factor that was able to account to any great degree for racial disparities was individual-level socioeconomic status. Accounting for this factor substantially reduced the disparity for Hispanics and other racial and ethnic groups (Asian Americans and American Indian/Alaska Natives) and eliminated the disparity for African Americans.
This finding suggests that something beyond structural features of access to care, or socioeconomic status, may be responsible for disparities in colorectal cancer screening. It also is consistent with conclusions from other studies.35,36
Some recent studies provide excellent insight into this problem. A recent qualitative study provided some explanation about how context may shape colorectal cancer disparities. In particular, the perception of risk for developing cancer may be shaped by the specific geographic context in which people live, which in turn influences health behaviors that include the likelihood of seeking appropriate colorectal cancer screening.40
In such a case, even if an individual had health insurance coverage, that person might not seek out colorectal cancer screening because of other structural or cultural barriers such as fear of medical encounters, stigma of colorectal endoscopy, low levels of health literacy, or lack of paid leave from work.
The findings from another recent study that examined the persistent disparity in colorectal cancer screening for Hispanics suggested that high levels of fatalism and low levels of health literacy might be responsible for low levels of colorectal cancer screening, at least among low-income Hispanics.41
Future research in this area may benefit from exploring how perceptions of risk and health literacy among racial and ethnic groups contribute to the likelihood of one’s being screened for colorectal cancer.