Colorectal Cancer Screening Use Among Insured Primary Care Patients

Colorectal cancer screening use was similar in 2 divergent primary care populations. Colonoscopy was the most frequently used modality; FOBT was used inconsistently.
Published Online: July 13, 2011
Deirdre A. Shires, MPH, MSW; George Divine, PhD; Michael Schum, PhD; Margaret J. Gunter, PhD; Dorothy L. Baumer, MS; Danuta Kasprzyk, PhD; Daniel E. Montano, PhD; Judith Lee Smith, PhD; and Jennifer Elston-Lafata, PhD

Objective: To compare colorectal cancer (CRC) screening use, including changes over time and demographic characteristics associated with screening receipt, between 2 insured primary care populations.

 

Study Design: Clinical and administrative records from 2 large health systems, one in New Mexico and the other in Michigan, were used to determine use of CRC screening tests between 2004 and 2008 among patients aged 51 to 74 years.

 

Methods: Generalized estimating equations were used to evaluate trends in CRC screening use over time and the association of demographic and other factors with screening receipt.

 

Results: Rates of CRC screening use ranged from 48.1% at the New Mexico site to 68.7% at the Michigan site, with colonoscopy being the most frequently used modality. Fecal occult blood test was used inconsistently by substantial proportions of patients who did not meet the definition of screening users. Screening use was positively
and significantly associated with older age, male sex, and more periodic health examinations and other types of primary care visits; at the Michigan site, it was also associated with African American race, married status, and higher annual estimated household income.

 

Conclusions: Among insured primary care patients, CRC screening use falls short. Further research is needed to determine what factors are barriers to routine fecal occult blood test or colonoscopy use among insured patients who have access to and regularly use primary care and how those barriers can be eliminated.

 

(Am J Manag Care. 2011;17(7):480-488)

Commonalities in colorectal cancer screening use were evident across 2 insured primary care populations.

 

  • Between one-third and one-half of patients at each site were not up-to-date with screening.

 

  • At both sites, younger patients, female patients, and patients with fewer periodic health examinations and other types of primary care visits were at greater risk of being unscreened for colorectal cancer.

 

  • Among recommended testing modalities, colonoscopy was by far the most used test among patients who were up-to-date with screening.

 

  •  Although fecal occult blood test use was common, adherence to annual testing was a challenge at both sites.
Colorectal cancer (CRC) screening was first recommended by professional organizations for average-risk adults 50 years and older more than 2 decades ago.1-5 Most recently, the US Preventive Services Task Force4 issued evidence-based CRC screening guidelines recommending the use of the following: (1) fecal occult blood test (FOBT) or fecal immunochemical test annually, (2) FOBT or fecal immunochemical test every 3 years combined with flexible sigmoidoscopy every 5 years, or (3) colonoscopy every 10 years. Despite these guidelines and the availability of several effective screening tests, CRC screening remains underused.

Population-based surveys indicate that CRC screening rates have increased steadily over time,6-8 with the most recent estimates showing that screening rates exceed 60%.7,9 Less recently, claims-based and medical record–based studies among insured populations point to similar trends but tend to place estimates of the screened population somewhat below those obtained by self-report10,11 and indicate an increase in the use of colonoscopy relative to other modalities.12,13

Using automated claims and electronic medical record data for a 5-year period ending December 31, 2008, we compared CRC screening use between insured primary care populations receiving care from 2 large integrated delivery systems, one located in southeast Michigan and the other located in central New Mexico. We report annual screening use by modality between 2004 and 2008 and examine demographic and other patient factors associated with screening receipt.

METHODS

Study Settings and Samples

Eligible patient populations were selected from those receiving primary care at 2 health systems. The Michigan health system includes a 900-member multispecialty salaried medical group that staffs 27 primary care clinics in Detroit and surrounding communities. The New Mexico health system is the largest physician-owned multispecialty physician group in the state, with 230 salaried physicians and 70 midlevel care providers. It staffs 10 primary care clinics in Albuquerque and surrounding communities. Both sites are participating in a Centers for Disease Control and Prevention–sponsored randomized controlled trial evaluating an intervention to increase CRC screening among primary care patients. These 2 health systems were chosen for trial participation because they have a large number of eligible patients and

physicians, a high proportion of minority patients, and strong research capacity and data capture capabilities.

Patients eligible for study inclusion were those aged 51 to 74 years on December 31, 2008, and continuously enrolled in a system-affiliated health maintenance organization during the 5-year study period ending December 31, 2008 (ie, the 5-year period preceding intervention implementation). To our knowledge, no randomized controlled trials to increase CRC screening took place at either health system during the study period. All patients with health plan enrollment were eligible regardless of whether their coverage was sponsored by employer, Medicare, or other. Although Michigan patients had copayments for office visits, they had no cost sharing specific to CRC screening tests. New Mexico patients may have had a deductible, minimal copayment, or both for endoscopy procedures depending on their personal coverage and situation. Eligible study patients also had at least 1 primary care visit during the study period (2004-2008). Exclusion criteria included evidence of a history of colorectal carcinoma, ulcerative colitis, Crohn’s disease, or bowel resection. The study was approved by the institutional review board at each participating site.

Data Sources and Measures

Automated health system records were used to obtain patient age, sex, race (Michigan site only) or ethnicity (New Mexico site only), residential street address, marital status (Michigan site only), primary care visit frequency, diagnoses, and receipt of CRC screening tests. At the Michigan site, race is recorded as 1 ethnicity was determined using GUESS (Generally Useful Ethnicity Search System), which identifies ethnicity based on surname. GUESS has been shown to be 90% accurate for identifying individuals of Hispanic ethnicity in New Mexico.14

Residential street address was combined with zip code–level data for 2009 from the Current Population Survey to construct an annual estimated household income for patients.15 Inpatient and outpatient International Classification of Diseases, Ninth Revision, Clinical Modification diagnostic codes during the 5-year period were used to construct an adapted Charlson Comorbidity Index.16 Current Procedural Terminology codes were used to categorize primary care visits during the 5-year period as periodic health examinations (PHEs) or as other types of primary care visits.

We calculated annual testing rates for FOBT, colonoscopy, flexible sigmoidoscopy, double-contrast barium enema, combination of FOBT and flexible sigmoidoscopy, and other modality combinations for 2004 through 2008. Five-year CRC screening receipt was based on the 2002 US Preventive Services Task Force guidelines.17 Patients who received at least 3 FOBTs (>10 months apart) or 1 colonoscopy, flexible sigmoidoscopy, or double-contrast barium enema during the 5-year period were considered screening users. Patients with evidence of colonoscopy receipt between 1999 and 2003 were also considered screening users.

Statistical Analysis

Characteristics of patients receiving care from the 2 health systems were compared using X2 test for differences in proportions, t test for differences in age, and Wilcoxon rank sum test for differences in annual estimated household income and primary care visit frequency. For the analysis of time effects, year was represented by 4 indicator variables, and an overall 4-df test for year effect was performed. For analyses of withinsystem effects, generalized estimating equation logistic regression models were used to account for the nesting of patients receiving care from the same primary care provider. For differences in screening use by patient characteristics, generalized

estimating equation logistic regression models were used for each characteristic by itself and after adjustment for patient age, sex, race/ethnicity, annual estimated household income, frequency of PHEs and other types of primary care visits, and Charlson Comorbidity Index. The Michigan health system models were also adjusted for marital status.

RESULTS

Cohort Characteristics

In Michigan, 13.5% of the cohort were older than 65 years, and 54.1% were female (Table 1). Approximately one-third of patients (37.1%) were African American. Most patients (73.4%) were married, and the mean annual estimated house-communities of residence was $76,846. Sixty-three percent of patients had at least 1 PHE during the study period, and 37.0% had at least 2 PHEs in the 5-year period. Compared with Michigan patients, New Mexico patients were significantly older (P <.01) and were more likely to be female, reside in areas with lower annual estimated household income, and have fewer primary care visits. hold income in their communities of residence was $89,809. Most patients (63.4%) had at least 1 PHE during the study period (2004-2008), with 44.0% having at least 2 such visits.

In New Mexico, 46.8% of patients were older than 65 years, and 57.0% were female, while approximately one-third of patients (36.2%) were of Hispanic ethnicity (Table 1). The mean annual estimated household income in their  communities of residence was $76,846. Sixty-three percent of patients had at least 1 PHE during the study period, and 37.0% had at least 2 PHEs in the 5-year period. Compared with Michigan patients, New Mexico patients were significantly older (P <.01) and were more likely to be female, reside in areas with lower annual estimated household income, and have fewer primary care visits.

Annual CRC Screening Use

As summarized in Table 2, annual CRC screening use (overall and for specific modalities) varied by year at both sites (P <.01 for all). At the Michigan site, the overall annual CRC screening rate increased steadily between 2004 and 2008. Annual use of colonoscopy increased between 2004 and 2007, and annual use of FOBT increased between 2005 and 2008. At the New Mexico site, the overall annual CRC screening rate increased between 2004 and 2005 and declined thereafter. Annual colonoscopy and FOBT use among New Mexico patients paralleled this overall pattern. At both health systems, only the use of colonoscopy alone or FOBT alone contributed substantively to the observed annual use of screening.

Five-Year CRC Screening Use

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