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:21 March 2014
Reviewer: Tim Benning
Reviewer's report:
Dear editor and authors,
Thank you for the opportunity to review the manuscript of Andreas Adler and
colleagues. I have carefully read the authors’ work entitled “Improving
compliance to colorectal cancer screening using blood and stool based tests in
patients refusing screening colonoscopy in Germany”.
The paper is well written, the title is ok, the paper contains several interesting
results, the data seem to be sound, the conclusions adequately support the data,
and the authors gave an acceptable overview of studies. I particularly like the
finding that, in a German context, people prefer blood-tests over stool-tests as
this provides highly relevant information about how to successfully increase
uptake of colorectal cancer screening. Another strong point of this research is
that it also measures the reasons why respondents have chosen for a particular
test by means of ranking-based tasks. In these tasks respondents were asked to
rank in order possible reasons why they had decided not to do a colonoscopy,
why they had chosen a blood test, and so on.
However, the research also has several limitations. The first major limitation is
that the methods used are rather simple and that they could be described better.
The second major limitation is that the discussion section could be improved. The
authors should definitely put more emphasis on describing the limitations of the
study. One issue that could be addressed, for example, is that the sample may
be biased. Looking at Tables 1 to 4, I am not sure whether the sample represents
the target population for CRC screening in Germany. Maybe the authors could
elaborate on this issue. In other words, is this sample representative, and if not,
how much do they expect that this affects the final results (e.g. the percentage of
choices for blood versus stool-tests)?
Overall, my attitude towards the manuscript is favorable. The practical relevance
of this work compensates the unsophisticated character of the research methods
used. However, in my opinion, there are several major revisions needed before
the manuscript can be accepted for publication. To improve the paper, I have
several suggestions that are based on improving the abstract, the methods used
and how they are reported, and the discussion section (with special attention to
the limitations of this work). Following the journal’s guidelines, I made a
distinction between major, minor and discretionary revisions, these can be found
below.
Major revisions
- It would be helpful for the reader to mention the specific objective(s) of the
paper in the first paragraph of the abstract (page 2, line 4). From the abstract, it
is not directly clear what the specific goal of the paper is.
- The authors should be somewhat more specific in describing the type of
method used in the second paragraph of the abstract (page 2, line 5). Now, it just
seems a recording of several socio-economic factors. I am not completely sure,
but can this research be presented as some type of experiment? Another idea is
to also mention that ranking tasks are used for the possible explanations why
respondents do not choose for non-invasive tests (see the paper’s additional
files).
- On page 3 (lines 34-43) the authors inform the reader about CRC screening in
Germany. However, there is no information whether this concerns
campaign-based screening. Is there a national CRC screening campaign in
Germany that is repeated over years? It could help the reader to add some
information about this.
- On page 5 (lines 73-77) the authors explain how subjects were recruited during
regular consultations with primary care physicians or company doctors, that 174
CRC screening eligible subjects were enrolled, and that all subjects were advised
to undergo screening by colonoscopy. Was this advice based on bowel
complaints or just because they are above a certain age and therefore belong to
the target group for screening? I could not find any information about this, please
clarify.
- Is this the first time (study) that a choice for a blood-test was offered instead of
a stool-test in Germany (Page 5, line 79) or were there other types of blood-tests
used before? Please explain.
- Maybe the authors could report some information, if available, about the
sensitivity and specificity of the specific blood test described in the article?
- On page 6 (line 96) the authors wrote that demographic data is summarized in
table 1. It would be good to add some text to describe these sample
characteristics. Even more important, some text should be added about a
comparison of these sample characteristics with the characteristics of the general
target population for CRC screening in Germany. The education level of the
sample seems to be high, the number of females is relatively large, and there are
other examples like these. In other words, it would good to discuss the possibility
of sample bias in the discussion section and to elaborate on how this may have
affected the results (e.g. the percentage of choices for blood versus stool-tests).
This also holds for the information in tables 2-4. The respondents in the sample
do exercise a lot, is this more than average? Furthermore, respondents’ prior
knowledge about fecal occult blood testing and colonoscopy also seem to be
large. Interestingly, only significant differences are found for exactly these
variables (p.6 lines 101-103).
- On page 6 (line 115) the authors quickly refer to tables (S1-S11). Maybe more
text can be added to also describe some other findings from these tables.
- It may be interesting to analyze the impact of the demographics on the choice
of non-invasive test by means of a logit model. Are the same variables significant
in such an analysis?
- The authors explained the standard recommendation script (page 7 lines
122-124). Is this the general German recommendation standard or just for this
“experiment”? Please clarify
- The acceptance rate (page 7 line 127) for colonoscopy was higher (37%) in this
study than the overall reported German population rate (25%), can this be due to
the specific sample used? This could also be discussed.
- I am not sure if it is common to present the findings of Chi-squared tests in a
figure like Figure 2. As far as I understand, the figure only shows the significance
levels of all variables (which are already reported in the text of the paper for
significant variables). It may make more sense to report the Chi-square test more
precisely instead of only the p-values as in Figure 2. Maybe delete Figure 2.
- The authors could think about some additional limitations of the study such as
the representativeness of the sample (see earlier comment), more emphasis
could also be given to the small sample size in combination with the reliability of
the Chi-Square tests.
Minor revisions
- I would replace “far too low” with “too low” (p.3, line 32)
- Page 6 (line 95) “for a screening colonoscopy” should probably be “for
screening colonoscopy”
- On page 6 line 111 the second reason for rejecting colonoscopy is described as
“fear of colorectal cancer itself”, whereas in Table S-1 this is described as “I am
not comfortable with the test or with the subject “colon cancer”. Maybe this could
be reworded.
- Page line 128 “There are only a few reports …” should be a new paragraph.
- Page 7 line 135 “who completing” should probably be “who completed”.
Discretionary revisions
- The tables in the supplementary files are interesting, but the rank is only
determined here based on the percentage of respondents who ranked a
particular aspect as most important (if I am correct). Borda scores could also be
used to say something about the relative importance of the answers in the
ranking task, does this produce different results? See, for example, Dolan P,
Tsuchiya A. Health priorities and public preferences: the relative importance of
past health experience and future health prospects. J Health Econ 2005; 24:
703-714.
- The authors could add that their work builds on the study of Benning et al.
(2014) in which it is found that the Dutch target population prefers a blood-test
above a stool-test for campaign-based CRC screening and that offering multiple
screening tests can improve screening participation. Benning et al. (2014) is
based on a discrete choice experiment and measures stated preferences. It is
interesting to read that this article measures respondents’ actual preferences in a
German context and that the results are comparable between studies. The
reference is: Benning TM, Dellaert BGC, Dirksen CD, Severens JL. Preferences
for potential innovations in non-invasive colorectal cancer screening: A labeled
discrete choice experiment for a Dutch screening campaign. Acta Oncologica
2014; DOI: 10.3109/0284186X.2013.877159.
Kind regards,
Tim M. Benning
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Needs some language corrections before being
published
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