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1 University of North Texas Health Science Center at Fort Worth, Primary Care Research Institute, Fort Worth, Texas
CORRESPONDING AUTHOR: Roberto Cardarelli, DO, MPH, UNTHSC, Primary Care Research Institute, 855 Montgomery, 2nd Floor, Fort Worth, Texas 76107, rcardare{at}hsc.unt.edu
| ABSTRACT |
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METHODS Self-reported data were obtained from the United States 2004 Behavioral Risk Factor Surveillance System. Men and women aged 50 years and older were included, and associations of having a personal health care provider, age, sex, race/ethnicity, education, income, and health insurance status with colorectal cancer testing were examined. Multiple logistic regression was performed on a final sample of 120,221 individuals.
RESULTS Having at least 1 personal health care provider significantly predicted up-to-date colorectal cancer testing in both the univariate (odds ratio [OR]=3.96; 95% confidence interval [CI] 3.56–4.41) and multiple regression models (OR = 2.91; 95% CI 2.58–3.28). Age, sex, race/ethnicity, education, income, and health insurance were also significantly associated with up-to-date colorectal cancer testing.
CONCLUSIONS Having a personal health care provider was associated with up-to-date colorectal cancer testing. Efforts to increase and support the primary care workforce are needed to improve up-to-date colorectal cancer screening rates.
Key Words: Health care delivery health services research primary health care access to health care health services accessibility colorectal cancer health promotion screening
| INTRODUCTION |
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That primary care has a positive effect on population health has been shown in a landmark study by Starfield et al,3 who found access to primary care prevents illness and death and results in more equitable health. In a preventive health care delivery system that some believe is fragmented and fundamentally flawed,4 the Starfield et al findings lend support to improving rates of preventive health care screening. One such preventive screening test is for colorectal cancer. Colorectal cancer has garnered particular attention because it has low screening rates among men and women (approximately 50% in the United States) and accounts for 1 of the top 3 causes of cancer deaths.5–7 Moreover, persistent colorectal cancer disparities exist, with African Americans suffering 15% and 40% higher incidence of and mortality from colorectal cancer, respectively, than whites.8–13
Further studies with a sample representative of the US population are needed to assess whether access to primary care clinicians improves colorectal cancer screening rates beyond changes in socioeconomic factors and health insurance status. Hence, the purpose of our study was to assess the relationship between having a primary care clinician and up-to-date colorectal cancer testing after controlling for age, sex, race/ethnicity, education, income, and health insurance status using a national data set involving all 50 states.
| METHODS |
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Inclusion Criteria
The study included respondents from the 50 states that administered the 2004 BRFSS core module. Colorectal cancer screening starts at age 50 years, so we used data from respondents aged 50 years and older. Because we used 2004 BRFSS data, we followed the 2004 US Preventive Task Force recommendations. No maximum age was selected, as there were no definitive recommendations on this issue in 2004.
Dependent Variables
The outcome of interest was derived from responses to the colorectal cancer screening section. Respondents were asked 4 questions and were considered to be up-to-date if they had a fecal occult blood test within the previous year or had a sigmoidoscopy or colonoscopy within the previous 10 years. The BRFSS colorectal cancer screening questions did not allow sigmoidoscopy and colonoscopy to be separated as discrete tests, nor did it ask about double-contrast barium enema testing. The response was dichotomized as either "testing up-to-date" or "testing not up-to-date." The term screening was avoided in this study, because the BRFSS questions did not ask whether respondents received a colorectal cancer test for screening or diagnostic purposes. Nonetheless, a colorectal cancer test use was conceptualized as a proxy for screening.
Independent Variable
The primary independent variable was based on the question, "Do you have 1 person you think of as your personal doctor or health care provider?" Responses included "yes, only 1," "more than 1," or "no." It should be noted that the BRFSS did not differentiate among non–primary care clinician, primary care physician, or primary care mid-level clinician; hence, personal health care provider was the preferred term in this study to mirror the question that was asked in the BRFSS. Personal health care provider, however, is conceptualized as a proxy measure for primary care clinician in the current study, especially for responses that included "yes, only 1," because these responses reflect a more traditional primary care relationship. After missing data for personal health care providers were taken into account, there were 144,897 individuals remaining in study.
Covariates
The covariates included (1) age, (2) sex (male or female), (3) race/ethnicity (non-Hispanic white, non-Hispanic African American, non-Hispanic other, non-Hispanic multiracial, and Hispanic), (4) education level (not a high school graduate, high school graduate or greater), (5) annual household income level (less than $25,000, $25,000 or greater), and (6) having health insurance (yes or no).
Analysis
Descriptive statistics were calculated for the participants using weighted population percentages.
2 Statistics and analyses of variance were used to test for differences between having a personal health care provider and categorical and continuous variables, respectively. Univariate logistic regression analyses were conducted to determine the association between the dependent and independent variables. Next, multiple logistic regression analysis was conducted to control for confounding covariates. Covariates that were significantly associated with up-to-date colorectal cancer testing or known as independent predictors in previous studies were included in the multiple logistic regression model.
Unadjusted and adjusted odds ratios and 95% confidence intervals were calculated for the univariate and multiple logistic regression analyses, respectively. Tests for collinearity were conducted, and no collinear relationships were identified in the final model. Interactions terms using "having a personal health care provider" and each covariate were introduced into the final model, none of which were found to be statistically significant.
The final sample size used in the multiple logistic regression analysis included 120,221 individuals after missing data were taken into account. All analyses were conducted using the Complex Sample Module, SPSS version 14.0 (SPSS, Inc, Chicago, Illinois, 2005), and the stratum, primary sampling units, and weights to take account of the complex sample design. Details of how weighting was calculated have been described in detail elsewhere.14
| RESULTS |
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| DISCUSSION |
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Nonetheless, the findings of this study do not diminish that being up-to-date in cancer screening is a multifaceted problem, because this study does not account for patient-level, clinician-level, and environmental-level factors.24–33 The purpose of our study was to assess system-level factors that are known to contribute to health care delivery outcomes, such as cancer screening. Previous studies have found patient-level factors (ie, lack of knowledge),24,25 clinician-level factors (ie, offering colorectal cancer screening),22,26–28 socioeconomic factors (ie, education, income),29–31 and system-level factors (ie, health insurance status)32,33 to be barriers and facilitators to colorectal cancer screening. Ross et al found lack of health insurance to be associated with a significant decrease in use of preventive services.34 Their study, however, did not assess whether having a primary care clinician moderated the results. In fact, an assumption is often made in most health service studies that health insurance status and having a primary care clinician are proxy measures of a similar construct. Another study by Etzoni et al concluded that insurance coverage and having a usual source of care were the most important predictors of colorectal cancer testing.32 They used a composite measure that included both variables in their study, however, which made it difficult to assess the independent effects of each factor on colorectal cancer screening. A study of more than 55,000 women enrolled in the Womens Health Initiative Observational Study found having a usual source of care to be one of the strongest predictors in colorectal cancer screening after accounting for multiple variables, including insurance status and type.30 The present study corroborates these findings in that health insurance status and having a personal health care provider function as 2 independent factors affecting up-to-date colorectal cancer testing.
Eradicating health disparities is a primary Healthy People 2010 objective, and creating evidence about contributing factors may result in health-policy-driven solutions.35 Shi et al conducted an ecologic study that found primary care had an impact on health indicators by modifying the adverse effect of income inequality.36 The results of our study support this conclusion as well. Non-Hispanic African Americans were significantly less likely to be up-to-date for colorectal cancer testing in the univariate analysis; however, non-Hispanic African Americans were significantly more likely to be up-to-date for colorectal cancer testing compared with non-Hispanic whites after controlling for having a personal health care provider, education, income, age, sex, and health insurance status. A study by Coughlin et al found that differences between whites and blacks in having a fecal occult blood test within the past year in the southern United States no longer existed after accounting for the studys covariates, including health insurance status and seeing a physician within the past year.37 In fact, seeing the physician was the greatest predictor of having the screening test.
There are several limitations to this study. As with any self-reported survey, the data are subject to recall and other biases, including overreporting cancer screening status.38 The possibility exists for incorrect interpretation of questions, variations in interview techniques, nonresponses, and data-coding errors. In addition, although telephone surveys are easy to conduct and cost-effective, they may introduce potential biases. Those households without a home telephone are more likely to include persons who have lower incomes and less education, who live in rural areas, and who are in poor health, which casts doubt on the generalizability of the findings to the national population. The BRFSS accounts for such variance by poststratification and weighting adjustments to the data. It also attempts to minimize such errors by using a large sample size, as well as imposing quality assurance measures. In addition, as mentioned earlier, personal health care provider does not differentiate primary care from non–primary care or physician from mid-level clinicians. The authors stratified the response of having a personal health care provider as "1," "more than 1," and "no" to identify a more traditional primary care relationship (ie, having 1 primary care clinician). Another consideration is that selecting "more than 1" may indicate 2 primary care clinicians working in the same clinic or 1 being a specialist, especially among older responders. Although we do not feel this factor affects the overall findings or conclusions of the study, it is worth noting.
This study attempted to mirror the 2004 US Preventive Services Task Force recommendations (because the 2004 BRFSS was used) for colorectal cancer screening,39 but the BRFSS questions did not include barium enema testing and did not distinguish sigmoidoscopy from colonoscopy testing, because recommended screening intervals differ (5 years vs 10 years, respectively). A common limitation to research using secondary cross-sectional data is the inability to correctly assess up-to-date vs adequacy of colorectal cancer screening. For example, a 70-year-old man who had a fecal occult test within the last year would be classified as up-to-date but not necessarily adequately screened. If this screening test was his first for colorectal cancer (by any modality), he technically would have been inadequately screened, because testing should have commenced at the age of 50 years with appropriate follow-up intervals. In addition, as discussed earlier, the BRFSS colorectal cancer questions asked about test use but did not differentiate the purpose of having the test(s) (screening or diagnostic). Further studies are needed that investigate colorectal cancer screening and diagnostic testing separately. Finally, the cross-sectional nature of this study precludes any determinations of causality.
| FOOTNOTES |
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Disclaimer: The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Center on Minority Health and Health Disparities or the National Institutes of Health.
Funding support: The project described was supported in part by grant number P20MD001633 from the National Center on Minority Health and Health Disparities.
Received for publication February 19, 2008. Revision received May 27, 2008. Accepted for publication June 30, 2008.
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