Report in English with a Dutch summary (KCE reports 45A)

96 Screening for Colorectal Cancer KCE reports vol.45
screening behaviors 408, 415, 424, 433-439: e.g. perceived susceptibility 414 and
barriers 435, social 440, 441, cognitive 429, attitudinal variables 440, personal moral
obligation - I think I should have a screening test 429, etc. However, because of
the small number of studies, findings are best viewed as hypothesis generating.
Studies of interventions to modify risk perceptions provided some support for
the view that they are modifiable 442-446, 439, but there was conflicting evidence
that these changes were related to subsequent cancer screening. Methodologic
studies of how best to measure perceived risk are needed. Because most data
on the correlates of perceived risk were cross-sectional, it is difficult to
determine whether perceived risk is a cause or an effect in relation to cancer
screening. Longitudinal studies that measure perceived risk in defined
populations with different cancer screening histories and that include follow-up
for screening and repeated measurements of risk perception are needed to
clarify this relationship.
5.7.3 Factors influencing CRC screening adherence
5.7.3.1 Systematic review on participation in CRC screening (JNCI, 1997)
In a 1997 JNCI systematic review 403 more than 132 empiric studies were
included to evaluate the published literature on adherence to CRC screening
with either FOBT or sigmoidoscopy. Specifically, the review addressed the
following questions: 1) prevalence of FOBT and sigmoidoscopy; 2) interventions
to increase adherence to FOBT and sigmoidoscopy; 3) correlates or predictors
of adherence to FOBT and sigmoidoscopy; and 4) reasons for nonadherence.
Although selection criteria varied somewhat for the four questions, at the
minimum, the investigators had to describe the study population, the setting,
and the data collection methods. Because this was the first systematic review of
the topic, a wide range of study designs, varying in rigor, was included.
Study characteristics included program circumstances where all eligible persons
were offered a test (including the study arm of randomized clinical trials on
FOBT efficacy), intervention studies of methods to increase adherence as well
as intervention studies to evaluate the effects of diet restrictions, length of
testing, or type of test on adherence.
Population characteristics included patient populations, community-populations,
worksite populations and others (e.g. FDRs of CRC patients and other
volunteers, high-risk patients, members of voluntary organizations, etc.). In a
few reports, the study population was not clearly described.
Most studies measured behavior prospectively in response to an invitation to
undergo CRC screening. Community-based studies were further classified as
media campaigns or surveys. In media campaigns, persons were offered an
opportunity to pick up a kit, or kits were handed out to all comers in a
variety of settings, e.g., shopping malls and drug stores. Surveys measured selfreported
past behavior using different time periods, e.g., ever use or use during
the past year.
Overall, 101 studies reported adherance to CRC screening; 11 studies (231.365
individuals) examined adherence rates for FOBT re-screening; 22 studies (at
least 75.790 individuals) reported adherence rates for screening sigmoidoscopy;
3 studies (at least 8.672 individuals) assessed adherence rates for sigmoidoscopy
re-screening; and 18 studies (at least 74.677 individuals) reported adherence
rates following interventions to increase screening results. The numbers of
individuals in the remaining studies were not specified in the review.