Our primary finding is that rural-residing adults in the United States face significant and persistent disparities in colorectal cancer screening compared with their urban counterparts. This disparity is largest in remote rural areas, where the screening rate is roughly 17% lower than urban areas. Although overall colorectal cancer screening rates increased during the time of our study, screening rates for both urban and rural populations remained well below the target of 70.5% outlined in Healthy People 2020. Because screening has been shown to reduce colorectal cancer morbidity and mortality [19
], missed screening opportunities may lead to poorer colorectal cancer outcomes.
This rural disparity in colorectal cancer screening may be a result of several factors affecting rural populations. Distance barriers, financial barriers, such as high rates of uninsurance, and lack of physicians in many locations all reduce rural residents access to primary care – one of the strongest predictors of up-to-date screening status [24
]. Additionally, one screening modality, colonoscopy, typically requires access to specialist physician care, namely gastroenterologists, general surgeons, or gastrointestinal surgeons. Access to all of these specialist types is lower in rural areas compared with urban areas [26
]. Thus, efforts to increase colorectal cancer screening in rural areas may need to focus on access to both primary and specialty care.
Evidence gathered by the United States Preventive Services Task Force suggests that all three recommended screening strategies result in similar reductions in colorectal cancer incidence and mortality [2
]. To better understand the use of different types of screening tests in rural and urban areas, we separated noninvasive testing (fecal occult blood test) from invasive screening (flexible sigmoidoscopy and colonoscopy) and observed that lower uptake of invasive screening by rural adults explains much of the persistent rural–urban gap in colorectal cancer screening. Previous research has suggested that increases in overall colorectal cancer screening rates nationally are mostly attributable to increase in colonoscopy use [27
]. However, decreased access to specialty care in rural areas may prevent widespread adoption of this screening method in rural areas. To address this, one option may be to train more rural primary care providers to perform screening colonoscopy. This approach has been shown to be both safe and effective [28
]. However, there may be additional barriers to use of colonoscopy in rural areas, and thus, further research is needed to explore this.
In contrast to invasive screening, noninvasive FOBT use increased slightly in the rural population, while declining in the urban population over the study interval. Research at primary care practices has shown that patients have a preference for colorectal cancer screening by FOBT as opposed to invasive screening [29
]. Versus urban CRC screening programs, rural programs that provide a physician recommendation to utilize an FOBT, give FOBT education, or provide a FOBT kit from the provider to the patient are highly effective in increasing this screening method [30
]. Several studies have indicated that telephone counseling increases compliance for FOBT or fecal immunochemical testing (FIT), even in patients who were originally nonadherent [31
]. Additionally, in a study of low-income patients, those offered colonoscopy as the only screening method were less likely to adhere to screening recommendations than patients offered stool testing alone or a choice between the two [34
]. Thus, efforts to promote greater use of FOBT in rural primary care practice settings may be an effective and acceptable means of achieving the Healthy People 2020 objective. More research in this area is needed.
Our study has several limitations. Our findings are based on self-report of screening behavior. Although the sensitivity and specificity of self-report for colorectal cancer screening is high [35
], patients are more likely to underreport previous colonoscopy than previous stool testing. This may lead to underestimation of colonoscopy and flexible sigmoidoscopy rates relative to stool testing rates [35
]. Such bias, if present, would actually indicate that the rural–urban gap in colorectal cancer screening is greater than reported here, because urban populations have a higher prevalence of invasive testing. Another limitation of our study is questions proposed to participants ask only if they have had specific test, not the indication for the test. We assume that receipt of the test represented screening. This introduces potential misclassification bias, if diagnostic tests are being counted as screening tests. However, this is likely to affect both rural and urban populations equally, and therefore unlikely to affect the validity of our conclusions. Finally, the survey design combined colonoscopy and flexible sigmoidoscopy into one response, preventing us from separating these two mechanisms of testing. Because flexible sigmoidoscopy is often offered in a primary care office, and colonoscopy usually requires specialty care, the use of these two services may differ between rural and urban areas, but cannot be ascertained here.
Despite these limitations, our study highlights persistent disparities in colorectal cancer screening for rural residents of the United States. As compared with urban residents, rural residents had persistently lower colorectal cancer screening rates in the 7 years of this study, despite increasing screening rates overall. Remote rural residents consistently had the lowest screening rates of the groups studied. Clearly, efforts to eliminate this gap and achieve the Healthy People target in rural areas are needed. Furthermore, exploration of patient and system level factors that may be contributing to the measured disparities is important in developing programs to improve colorectal cancer screening in rural populations.