Review for 10.1186/1471-230X-14-183 (2014)

Reviewer's report
Title:Improving compliance to colorectal cancer screening using blood and stool
based tests in patients refusing screening colonoscopy in Germany.
Version:1Date:9 April 2014
Reviewer: Lina Jansen
Reviewer's report:
The authors of this study assessed the compliance to screening colonoscopy
and, in case of refused colonoscopy, the compliance with non-invasive tests
(stool or blood-based) in a sample recruited during regular physician
consultations in Germany. The study includes an analysis of factors associated
with the choices made by the participants. Results show that almost all
participants who refused colonoscopy accepted non-invasive methods. Plasma
testing was preferred mainly due to convenience. Strengths of the study are the
detailed assessment of preferences of the participants and of factors that might
be associated with the test choice. The main limitations of the study are the small
sample size that hampers the interpretation of the results and the lack of
information on representativeness of the study sample.
Major Compulsory Revisions
1. The authors state that subjects were recruited during regular consultations
with primary care physicians or company doctors but do not state
inclusion/exclusion criteria and response rates. To determine whether the sample
is representative more information is needed: a) How many physicians and
doctor’s practices participated? b) How were participating doctor’s practices
selected? c) Were all patients who had a consultation in the doctor’s practice
during a specific period asked for participation? d) How many patients denied
participation?
2. In addition to providing the above described information, it should be
discussed whether the sample is representative and whether specific biases
might exist. It should also be discussed why the rate of acceptance for screening
colonoscopy was higher in this study than in a previous report (line 126-127). Are
the characteristics of the study populations comparable?
3. In line 74, the authors write that CRC screening eligible subjects were
enrolled. In Germany, colonoscopy is covered for patients aged 55+, but the
study includes patients that are younger than 55 years. Why are these subjects
included? Are they screening eligible because of having symptoms or because of
having family predispositions? I think that reasons for colonoscopy for such
subjects are different than for subject who come for regular screening. The
authors should clarify this aspect and perhaps exclude participants who were
younger than 55 years or were offered colonoscopy due to specific
circumstances.
4. A strong limitation of the study is the sample size that hampers interpretability
of the results. The main analysis is based on 109 patients who refused
colonoscopy. For some analyzed factors, many categories were distinguished
leading to very small subgroups. I would suggest summarizing some subgroups
to reduce random fluctuation and, thus, improve the interpretability of the results.
Examples are: a) for ethnicity: German, Non-German, b) for profession:
employed, unemployed, retired, c) for health status: poor/good, d) for
self-evaluated risk of CRC: small/large, e) for alcohol consumption: two
categories, f) for smoking: two categories, g) for number of physician visits: < 15,
15+, h) for age: summarize <50 to 60 (or exclude < 55, see previous comments).
In addition, it would be helpful to include confidence intervals for the proportions.
Furthermore, the small sample size should be included as limitation in the
discussion.
5. Only univariate testes were made, which might lead to wrong conclusions due
to confounding. Due to the small sample size, computing large multivariate
models will not be possible. But I would suggest doing some age-adjusted
analysis, as age was significantly associated with refusing colonoscopy.
Furthermore, confounding should be discussed in the manuscript.
Minor Essential Revisions
Line 25/26: I would suggest using the latest estimates from Globocan 2012.
Line 34-36: The authors state that screening colonoscopy was introduced as a
covered option in 2002 but do not state whether gFOBT tests are also covered in
Germany. As the study participants have to choose between gFOBT or a
blood-based test, the manuscript should state whether the costs of the gFOBT
and the blood-based test are covered in Germany. Furthermore, it should be
stated whether the costs for the colonoscopy, gFOBT and blood test are covered
in the specific study. Costs for specific tests may influence the choice of the
participants.
Line 45: Delete the “,”
Line 62: I would suggest summarizing the performance characteristics of the
blood test in one sentence, as it helps the reader to interpret whether blood tests
may be a good alternative to the gFOBT without checking other literature.
Line 80: The authors wrote that approved descriptive material for each test was
given to the participants. Does the material include performance characteristics?
Such information might have strong impact on the decision of the participant.
Thus, I would suggest explaining in more detail what was included in the
material.
Line 101-103: The direction of the effect should be described. While there are
significant differences for amount of weekly exercise and education level, no
trend can be observed. This should be stated in the text.
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Acceptable
Statistical review: No, the manuscript does not need to be seen by a statistician.
Declaration of competing interests:
I declare that I have no competing interests.