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Volume
2:
No. 2, April 2005
ORIGINAL RESEARCH
Development of a Brief Survey on Colon Cancer Screening
Knowledge and Attitudes Among Veterans
Michael S. Wolf, PhD, MPH, Alfred Rademaker, PhD, Charles L.
Bennett, MD, PhD, M. Rosario Ferreira, MD, Nancy C. Dolan, MD,
Terry C. Davis, PhD, Franklin Medio, PhD, Dachao Liu, MA, June Lee,
Marian Fitzgibbon, PhD
Suggested citation for this article: Wolf MS, Rademaker
A, Bennett CL, Ferreira MR, Dolan NC, Davis TC, et al.
Development of a brief survey on colon cancer screening knowledge
and attitudes among veterans. Prev Chronic Dis [serial online] 2005 Apr [date cited]. Available from: URL: http://www.cdc.gov/pcd/issues/2005/
apr/04_0104.htm.
PEER REVIEWED
Abstract
Introduction
Poor knowledge of and negative attitudes toward available
screening tests may account in part for colorectal cancer
screening rates being the lowest among 17 quality measures
reported for the Department of Veterans Affairs health care system, the largest integrated
health system in the United States. The purpose of this study was
to develop a brief assessment tool to evaluate knowledge and
attitudes among veterans toward colorectal cancer screening options.
Methods
A 44-item questionnaire was developed to assess knowledge,
attitudes, and beliefs about colorectal cancer and screening and
was then administered as part of an ongoing randomized controlled
trial among 388 veterans receiving care in a general medicine
clinic. Sixteen candidate items on colorectal cancer knowledge,
attitudes, and beliefs were selected for further evaluation using
principal components analysis. Two sets of items were then further
analyzed.
Results
Because the Cronbach a for beliefs was low (a = 0.06), the
beliefs subscale was deleted from further consideration. The
final scale consisted of seven items: a four-item attitude
subscale (a = 0.73) and a three-item knowledge subscale (a = 0.59).
Twelve-month follow-up data were used to evaluate predictive
validity; improved knowledge and attitudes were significantly
associated with completion of flexible sigmoidoscopy (P =
.004) and completion of either flexible sigmoidoscopy or
colonoscopy (P = .02).
Conclusion
The two-factor scale offers a parsimonious and reliable
measure of colorectal cancer screening knowledge and attitudes
among veterans. This colorectal Cancer Screening Survey (CSS) may
especially be useful as an evaluative tool in developing and
testing of interventions designed to improve screening rates
within this population.
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Introduction
Colorectal cancer is the third most common cancer and the
third leading cause of cancer death in the United States (1). The
U.S. Preventive Services Task Force, the American Cancer
Society, and the American Gastroenterological Association
have developed guidelines for colorectal cancer screening and recommend
that persons aged 50 years or older who are at average risk for the disease be
screened periodically (2-4). Despite these recommendations and multiple studies
finding that colorectal cancer screening is cost-effective, screening rates are
the lowest for any other cancer screening test, with only half of persons aged
50 years and older having received any of the available methods (5).
One potential barrier to effective screening is inadequate
knowledge of both the disease and the possible options for
undergoing various types of screening tests (6-17). Poor
knowledge related to colorectal cancer is associated with
compromised perceptions of cancer risk and low rates of screening services use (6,7,12,14,16). Targeted efforts are needed to
improve both the overall awareness of colorectal cancer and the
availability of often limited resources for invasive screening
procedures, such as flexible sigmoidoscopy or colonoscopy. As health education
and colorectal cancer screening programs are developed, valid and reliable
measures of knowledge and attitude are needed to explicitly assess the efficacy
of these efforts.
One prior study reports on a brief instrument that measures beliefs and
attitudes toward colorectal cancer screening (17). This assessment was conducted
in a mailed survey of primarily white, employed men. However, it has not been
evaluated in other settings characterized by higher rates of racial/ethnic
minorities or among persons of lower socioeconomic status; these groups
have previously been found to be at greater risk for low screening compliance
(18-21). Another population at greater risk for low screening compliance is
veterans who receive care in the Department of Veterans Affairs (VA) health care
system, the largest integrated delivery system in the country. Out of 17 quality
measures routinely included in a nationwide VA quality improvement effort,
colorectal cancer screening rates are the lowest (22).
As part of a randomized clinical trial effort to improve colorectal cancer
screening rates within a VA
outpatient general medicine clinic, we recently reported on
knowledge and attitudinal barriers to screening participation
among veterans (23). Our intervention targeted improvements in
both veterans’ perceptions about the disease and screening
options in addition to their compliance. In this study, we developed
and validated a brief measurement tool for evaluating knowledge
and attitudes toward colorectal cancer screening among
veterans.
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Methods
Recruitment of participants
We designed a 44-item questionnaire to measure patient
knowledge, attitudes, and beliefs associated with colorectal
cancer screening and administered the questionnaire to 388
veterans. Male veterans aged 50 years and older who had not
received colorectal cancer screening (defined as having a fecal
occult blood test [FOBT] within one year or a flexible
sigmoidoscopy or colonoscopy within five years) were recruited from general
medicine clinics at the VA Chicago Health System between May 1, 2001, and
December 31, 2002. Patients were ineligible if they 1) had received a FOBT
within one year; 2) received a flexible sigmoidoscopy or
colonoscopy within five years; 3) had a personal or family
history of colorectal cancer or polyps; or 4) had a personal
history of inflammatory bowel disease. In addition, individuals
with dementia, impaired vision, hearing problems, or acute
illness were deemed ineligible to participate in the study. We
excluded patients with impaired vision because the instrument we
employed to assess health literacy required the ability to view a
list of words. The study protocol was approved by the
Northwestern University Institutional Review Board.
Between May 2001 and December 2002, research assistants approached 589
eligible participants as they waited for their scheduled
outpatient visit. Of these, 156 (26.4%) refused to be in the
study, and 56 (9.6%) did not complete the study questionnaire
primarily because their general medicine physician was ready to
begin their visit. In all, 388 (65.9%) individuals completed the
entire baseline interview, including the questionnaire. No
compensation was offered for participation. After the informed
consent process, participants took part in a 10- to 15-minute,
face-to-face interview that included sociodemographic items, a
literacy assessment, and the 44-item questionnaire. The literacy
assessment consisted of administering the Rapid Estimate of Adult
Literacy in Medicine (REALM), a screening instrument used to
determine the ability of patients to read and pronounce common
medical terminology and lay terms for body parts and illnesses
(24,25). Raw REALM scores are converted to grade ranges: 0–18
= third grade and below, 19–44 = fourth to sixth grade,
45–60 = seventh to eighth grade, and 61–66 = high school.
Follow-up interviews were conducted with 227 of these patients six to 12 months
after the baseline interview, beginning November 2001 through December 2003.
Patients’ screening status was obtained through medical record review also
during this period.
Development of the colorectal cancer questionnaire
The 44-item questionnaire included items designed to assess
knowledge of colorectal cancer and specific screening tests and
attitudes and beliefs toward colorectal cancer and available
screening options. Knowledge questions were adapted from the 1992
National Health Interview Survey (NHIS) Cancer Control
Supplement, with modifications to reflect current terminology
(e.g., use of the term flexible sigmoidoscopy or flex sig instead
of proctoscopy) (26). Attitudinal and belief items were developed
based on findings from focus groups conducted among this same
population of veterans (27). Reader comprehension of the
questionnaire items was evaluated using five one-hour cognitive
interviews among a convenience sample of community-based,
screening-eligible adults. All interviews were conducted by one
of the research investigators (Ferreira) and followed available
guidelines established for properly conducting cognitive
interviews in survey development (28). Interview techniques
included both “concurrent think-aloud” and specific probes. The
interviews were tape-recorded and abstracted for relevant
information, which was used to modify the questionnaire. The
modified questionnaire was then administered to a pilot group of
15 patients who were approached in the general medicine clinics
(29).
During the pilot process, we obtained patient feedback to
items in the pilot test and maintained reading levels of
instructions, items, and response options appropriate for
lower-literate patients; we used a common measure of document
readability (Flesch–Kincaid) to gauge reading levels. Principles
described by Doak et al were also applied to maximize
item comprehension (30). The final version of the questionnaire
registered as having a fifth-grade level of reading
comprehension. Even though we planned to administer the
instrument through an interview, the readability of the document
provided us additional assurance that the questionnaire could be
appropriately understood by most patients.
Of the 44 items in the questionnaire administered to the 388
veterans, 10 were associated with knowledge, 29 were associated
with attitudes, and five were associated with beliefs. After the
administration of the questionnaire, five of the knowledge items
were selected by the research team as appropriate for analysis;
other knowledge items were excluded because they were conditional
questions that were not answered by everyone. Of the 29 attitude
items, six were selected for analysis; again, other attitude
items were excluded because they were conditional questions not
answered by everyone. All five of the belief questions were
selected for analysis. Thus, a total of 16 items were selected
for analysis.
To prepare for data analysis, we scored questions so that low
values reflected high knowledge and attitudes consistent with
screening, or “correct” beliefs; high values
reflected low knowledge and attitudes inconsistent with
screening, or “incorrect” beliefs. Scoring for the knowledge scale
was dichotomous (1 = yes, 2 = no); a response of yes required follow-up patient
confirmation of understanding of the concept in question. For subjects who
responded no or who were determined to have inadequate knowledge of the test in
question, simple standard descriptions of both FOBT and flexible sigmoidoscopy
were provided by the interviewer to ensure a proper frame of reference. The attitude scale was scored from 1 to
3 on level of worry (1 = not very or not at all worried, 2 = somewhat worried, 3
= very or extremely worried). For both subscales and the total scale, the score
was determined by the sum of all nonmissing items. Items on the belief scale were scored for an initial analysis, but the
belief construct was not included in a final analysis.
Psychometric analyses
Principal components (PC) analysis was used to assess the
construct validity of the 16 items selected for initial analysis.
Cronbach a was used to examine reliability
(internal consistency) of the derived knowledge, attitudes, and
beliefs subscales. The value of Cronbach
a ranges between 0 and 1; if items within a scale are
perfectly correlated, then a = 1; if items are totally
unrelated, then a = 0. An α coefficient of 0.70 or higher
is considered to be acceptably reliable, indicating that items
within the same scale measure the same underlying construct. A
low Cronbach a for the belief scale and low factor
loadings of the belief variables resulted in deletion of this
subscale. Final PC analysis on the remaining seven knowledge and
attitude items was performed to determine whether these items
followed the knowledge and attitude pattern. To confirm
reliability of the knowledge and attitudes subscales,
correlations between the full scale and items within the
subscales were calculated.
An additional question of interest was: Do individuals who
improve their knowledge and attitude exhibit different screening
behavior than individuals who do not improve knowledge and
attitude? To assess the predictive validity of the total score
with screening behavior, change in the total score between two
time points (initial questionnaire and follow-up questionnaire)
was related to screening behavior using Fisher’s exact
test. It was postulated that an improvement in knowledge and
attitudes would be related to an improvement in screening
behavior.
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Results
Respondents had a mean age of 67.3 years (SEM = 0.52); 41.4%
were African American; 59.6% had completed high school, and 22%
had completed college. Respondents’ reading abilities
averaged at the seventh- to eighth-grade level (mean REALM score
= 57.3, SEM = −0.7), with 36% having reading skills lower than
the eighth-grade level. More than two thirds (69.1%) of the men
in the study were unemployed or retired, and 38% were married.
One third of respondents reported their health as either very
good or excellent.
Initial analysis consisted of the evaluation of 16
candidate items on colorectal cancer knowledge, attitudes, and
beliefs using PC analysis. Item factor loadings
for the three-factor solution are shown in
Table 1. Because
factor loadings for beliefs were low, the belief subscale was
deleted from further consideration. Also, decisions were made to remove
additional items based on lower factor
loadings and/or conceptual fit with remaining items. Thus, the items “likely to get a flexible sigmoidoscopy
(or FOBT) if friend recommended,” “know testing
age,” and “heard of colorectal cancer” were
deleted from further consideration.
The plan and procedure of item retention resulted in
provisional compositions that could be mapped to two factors:
knowledge and attitudes. These two sets of items were further
analyzed using PC analysis to assess construct validity and
Cronbach a to evaluate internal consistency (Table
2). All seven items were retained. The final scale consisted of
seven items: a four-item attitude subscale and a three-item
knowledge subscale (Table 3).
Higher correlations were observed between items within
subscales and their corresponding full scale, while low
correlations were expected and subsequently attained between
items within subscales and the noncorresponding full scale
(Table
4).
Twelve-month follow-up data were used to evaluate the
predictive validity of the knowledge and attitudes scale and each
of the two subscales for completion of a colorectal cancer
screening test (Table 5).
Because low values of all items in the
attitudes subscale reflected favorable attitudes consistent with
screening, and low values of all items in the knowledge subscale
represented high knowledge, decrements over time on these
subscales and the overall knowledge and attitude scale
represented an improvement in attitudes consistent with screening
and/or an improvement in knowledge.
We would assume such
improvements in knowledge and attitudes would be associated with
screening completion among eligible individuals noncompliant with
existing screening recommendations. A minimum decrement over time
(i.e., an improvement) of more than four points in the total
knowledge and attitude summary scale was significantly associated
with higher levels of colorectal cancer screening completion. A
decrease of more than four points over time on the full scale was
significantly associated with completion of flexible sigmoidoscopy (P = .004) and completion of either flexible
sigmoidoscopy or colonoscopy (P = .02).
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Discussion
We have developed a seven-item scale that can be used to
measure knowledge and attitudes toward colorectal cancer
screening among U.S. veterans. This instrument (Appendix),
the Colorectal Cancer Screening Survey (CSS), was designed to be
a brief and simple measure of knowledge and attitudes of veterans
toward colorectal cancer screening tests. The results of this
study suggest that the two-factor solution offers a parsimonious
and reliable measure. It is the first psychometric tool to our
knowledge to measure colorectal cancer screening knowledge and
attitudes among veterans, a population that is predominantly
low-income; nearly half in this study were African
American. The CSS was also developed for all levels of literacy.
Items were determined to be at a fifth-grade reading level and
had simple response options. Moreover, the instrument was
interviewer-administered.
Although adequate knowledge and positive attitudes alone may not
be sufficient to ensure completion of colorectal cancer screening
tests, both are common barriers that have been previously linked
to noncompliance. Several studies have found that the absence of
clinical symptoms was the most important factor associated with
noncompliance with returning FOBTs or undergoing a flexible
sigmoidoscopy procedure (7-16). Other attitudinal barriers
include fear and anxiety about cancer and perceptions that
colorectal cancer screening tests are uncomfortable,
embarrassing, or generally unpleasant. The goal of many
patient-directed interventions has been to overcome these
barriers; the CSS could serve as a valuable indicator of an
intervention’s efficacy to improve intermediary
outcomes.
Interestingly, the CSS had the highest predictive validity
with the completion of a flexible sigmoidoscopy screening test,
and was less likely to predict screening use when return of FOBTs
was considered. This discrepancy may reflect both the level of
difficulty of personal endorsement for colorectal cancer
screening participation between the available testing options, as
well as resources within the VA health care system. For example, the decision
to have an FOBT may depend less on knowledge and attitudes than the decision to
agree to a more invasive
procedure such as flexible sigmoidoscopy or colonoscopy.
It may be easier to agree
to complete an FOBT with poorer knowledge and a less positive attitude toward
colorectal cancer screening than to agree to complete a flexible sigmoidoscopy and colonoscopy, since
an FOBT asks less of a patient. Patients may complete the procedure based on
physician recommendation without recognizing it as a colorectal cancer screening
test. However, flexible sigmoidoscopy and colonoscopy procedures require repeat
visits and extensive preparation and take more time to explain and to
engage subjects in decision making. Although
the relationship did not reach significance, it is noteworthy
that those with improved knowledge and attitude scores on the CSS
scale had higher rates of colonoscopy screening, a test
that is often exceedingly difficult to receive in a timely manner within the VA
healthcare system because of limited trained clinical staff and resources.
Limitations to this study should be noted. First, our study is
based on a cohort of male veterans. Additional assessments in
other settings that provide care for large numbers of
racial/ethnic minorities, both male and female, and/or who are of
low socioeconomic status, such as the county medical systems, are
needed. Second, the CSS may benefit from further psychometric
evaluation that could improve upon the knowledge subscale and
also evaluate the reliability of CSS scores over time. Further
evaluation might also include test–retest reliability and discriminant validity assessments. Evidence of sensitivity to
change will be necessary to eventually determine whether the CSS
is an applicable evaluative tool for screening interventions.
In conclusion, the CSS may be a useful tool for testing the
effect of interventions designed to improve colorectal cancer
screening among veterans through improving patient knowledge and
attitudes. Because veterans with low knowledge and negative
attitudes toward screening tests may not be quickly or easily
identified in clinical settings, the CSS might eventually be
considered for use as a screening assessment to identify veterans
who are at risk for colorectal cancer screening
noncompliance.
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Acknowledgments
This project was funded by the Department of Veterans Affairs
(PCI 99-158) and the National Cancer Institute (R01 CA86424).
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Author Information
Corresponding Author: Michael S. Wolf, PhD, MPH, Assistant
Professor of Medicine, Institute for Health Services Research and
Policy Studies, Northwestern University, Feinberg School of
Medicine, 676 N St Clair St, Suite 200, Chicago, IL 60611. Dr.
Wolf is also affiliated with The VA Midwest Center for Health
Services and Policy Research, the VA Chicago Healthcare System,
Chicago, Ill, and the Robert H. Lurie Comprehensive Cancer
Center, Northwestern University, Chicago, Ill. Telephone: 312-695-0459. Email:
mswolf@northwestern.edu.
Author Affiliations: Alfred Rademaker, PhD, Feinberg School of
Medicine; Charles L. Bennett, MD, PhD, M. Rosario Ferreira, MD, The VA Midwest Center for
Health Services and Policy Research, Feinberg School of Medicine,
and Robert H. Lurie Comprehensive Cancer Center; Nancy C. Dolan, MD, Marian
Fitzgibbon, PhD, Feinberg School
of Medicine and Robert H. Lurie Comprehensive Cancer Center;
Terry C. Davis, PhD, Louisiana State University Medical School,
Shreveport, La; Franklin Medio, PhD, Medical University of
South Carolina, Charleston, SC; Dachao Liu, MA, Feinberg School of Medicine;
June Lee, The VA Midwest Center for Health Services and Policy Research.
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