Response to reviewers.
Please find attached a new version of the manuscript “Governance Quality Indicators
for National Organ Procurement Policies”. This new version addresses the questions
raised by the reviewers, as detailed below. Additionally, we have introduced unrequested
minor modifications to improve figures display and wording. We appreciate the comments
received, which gave us the opportunity to improve the original manuscript.
Reviewer #1:
“This is an interesting study addressing a fundamental problem in organ procurement
for transplantation, namely attitudes and education. The study has a number of strengths.
It is well written, in good English, and well reasoned. The number of respondents
is large although there is clearly a selection bias in terms of the demographics of
respondents. The questionnaire was comprehensive and well researched. The conclusions
are interesting and thought provoking, describing a novel form of governance. I would
raise the following observations”:
We appreciate Reviewer 1’s kind words about our manuscript. In the revised submission,
we have taken numerous steps to quantify the extent of gender imbalance, examine its
sources, and have also emphasized the limitations inherent to our convenience sampling
approach.
Major
The authors propose a novel tool for governance and then claim that their study, "validates
a tool for analyzing policy governance....". I do not believe that the tool has been
validated as there is no standard to validate against. This needs further discussion
and a proposal as to how it might be validated.
As Reviewer 1 notes, we did not assess the proposed tool’s validity or reliability.
We acknowledge that referring to our study as ‘validating’ the tool was misleading,
as there is no previous measurement of governance quality with which our results can
be compared. In the revised manuscript, we have replaced the term “validates” with
the unambiguous alternative “introduces”, e.g., in the Abstract:
(Abstract)
→ “Our study ‘introduces’ a tool for analyzing policy governance”).
The respondent population is highly selective which is acknowledged towards the end
of the manuscript but this needs more prominence. While the findings are interesting
to be conclusive this finding needs to be replicated in a more unbiased population
than largely female students in their twenties in large metropolitan universities.
This needs more discussion.
In the revised submission, we have clarified that we used a convenience sample and
have given more attention to the overrepresentation of women in our sample.
We clarify the recruitment method in the Abstract and in the Introduction, as follows:
(Abstract)
→ Methods: Between 2017-2019, we conducted a convenience sample survey of students
(n=2006)
(Introduction; Page 5)
→ “We do so by administering a survey to a convenience sample of university students
focusing on […]”
In preparation for our resubmission, we also conducted new analyses attempting to
diagnose the causes of such stark gender imbalance in our sample. As a result of these
analyses, we now claim in the paper that the high female-to-male ratio in the study
sample is due, to a certain extent, to the greater proportion of women already present
(a) in the sampling frame (i.e., the study programs from which we recruited our sample),
and also (b) in the population (i.e., tertiary education in Europe as a whole).
To support this, we first provide detailed information of the student gender distribution
in the sampling frame: i.e., for each participating university (when available) and
study field (health sciences on the one hand, and humanities, social sciences and
arts on the other) on the year when data collection took place. This information is
made available in the Supporting Information file as well as in the bottom of this
cover letter. Second, we provide more general information about gender distribution
in the population: i.e., drawing from Eurostat census information on tertiary education
throughout Europe. These explorations suggest that the gender imbalance in our sample
is not as pronounced as it might initially appear: The female-to-male ratio is 2.85:1
in our sample, and 2.15:1 in the population. In the revised manuscript, we suggest
that the remaining overrepresentation (relative to the population) can be accounted
for by known sex differences in non-response bias, since response rates have been
found to be higher among women than among men –at least for volunteer-based, survey
studies (REFERENCE ADDED). We highlight this potential limitation in the Introduction
(p6), in the Methods section (p12), and in the Discussion (p25), as follows:
(Introduction Pages 5-6)
→ “Our sample (n=2006) serves the purpose of testing the theoretical framework, but
the respondent population is highly selective and cannot be considered representative
of national populations, as discussed below”.
(Methods, Page 12)
→ “Overall, 2006 Austrian, Belgian, Danish, German, Greek, Slovenian and Spanish students
(age bracket (mode) = 20 to 24 years) took part in our study. A majority of them (74%)
were women (see Table 1), which partially reflects an overrepresentation of women
in the disciplines concerned [Supplementary file Table 1 ADDED] [REFERENCE EUROSTAT
ADDED], but may also account for an answer bias, as mentioned in the Discussion section”.
(Discussion, Page 25)
→ “Second, our sample shows a gender bias across all countries and study fields.
The fact that more women took part in the survey than did men can be partially explained
by high female-to-male ratios in the sampling frame (supplementary file) –particularly
among majors in health sciences (54-72%; vs 39-62% for humanities/social sciences)–
as well as in the European student population (72% for health sciences students; 64%
for humanities/arts/social sciences students; see [EUROSTAT, 2018]). Controlling for
the gender distribution in the population, we still observe some overrepresentation
of women in our sample, which may stem from sex differences in non-response bias,
previously detected in other studies [19, REFERENCE ADDED Damman et al] indicating
a higher retention and completion rates among women than men.”
We agree with Reviewer 1 that future work should conduct the same governance analysis
on the basis of representative panel data, as we mention in the Discussion (p27):
(Discussion, Page 26)
→ “Future work should use nationally representative population data to conduct the
same governance analysis”.
Despite the discussion of default options there should be some discussion addressing
the difference between "soft" and "hard" default options whereby next of kin can override
donors’ overtly expressed wishes.
Reviewer 1 is right that models of consent for organ procurement do not rely on default
options alone, but critically depend on the authority given to families as well. Consent
systems for organ recovery are indeed more complex than just default options, as their
implementation also depends on the available procedures to express individual preferences
and, even more importantly, on the authority given to the next of kin. This is partially
acknowledged in the introduction (p.2) and in the discussion section (p.25), where
we claim that:
“Consent policies for post-mortem OP establish how citizens may express their preferences
(e.g., donor and refusal registries, donor cards, etc.), next-of-kin’s role in OP
decision-making, and the default rule (retrieving or not retrieving the organs) when
no preference is available. Jurisdictions vary regarding the means of expressing individuals’
preferences and the authority of the family [5]” (p2)
“in most countries, the family of the deceased are allowed to make decisions over
OP when the deceased person had not [5]. This may reduce the risk of actual violations
of peoples’ autonomy to anecdotal incidence”. (p25)
Reviewer 1’s comment also underlies the distinction between “soft” consent systems,
(where family preferences are taken into account and are allowed to interfere with
the default option) and “hard” consent systems (where the default policy is applied
regardless of family preferences). We acknowledge that this distinction could be relevant
for our policy governance assessment. On the one hand, family involvement in the decision-making
process may determine the extent to which individual preferences and the autonomy
of the deceased is respected. On the other hand, individuals may fail to express their
preferences regarding organ retrieval if they believe their families will eventually
have a say in the decision, or even the last word.
Our model for policy governance assessment uses awareness of, and agreement with the
policy in force as indicators for governance quality. Unfortunately, this type of
policy analysis is not applicable, in the current state of knowledge, for family involvement
in decision making, for the following reasons:
To include the family dimension in our governance quality model, we would have had
to explore participants’ awareness of the role family plays in their country, and
their level of agreement with such policy. However, reliable information about the
role families play in each country is either ambivalent, contradictory, or simply
not available, thus making it impossible for us to assess whether individuals know
it. In a previous work, we have argued that the exact role families play in each jurisdiction
can hardly be captured by the twofold “hard/soft” dichotomy (Delgado et al 2019):
In fact, families may have four incremental levels of involvement in the organ retrieval
decision-making process: 1. they may have no role whatsoever, 2. they may only be
expected to witness or update the deceased’s preferences, 3. they may act as surrogate
decision-makers and decide on behalf of the deceased, and finally, 4. they may have
full decisional authority, meaning that they could override both a consent, and a
refusal (although there is no robust evidence that the latter ever happens). Even
more crucially for the purpose of including family decision-making in our governance
model, the classification of countries according to these four levels (or, for the
same purposes, according to the hard/soft dichotomy) depends on whether the focus
is placed on the authority families are given by law (de iure) or the authority they
actually have in practice (de facto). However, two of the authors have shown that,
in most countries, there is no correspondence between the official and the actual
role families play, the latter being only supported by partial and unreliable data
(Morla et al, forthcoming). To give a few examples, in Spain, Chile, and to some extent
in Austria, the law only gives families the authority to witness or update the deceased’s
preferences, but families may actually be allowed by doctors to have the last word
(meaning that they can in practice overrule the deceased’s consent to donate) (Delgado
et al. 2019). Another example is France, where a recent law has been enacted to avoid
family veto, but there is evidence suggesting that doctors still prefer not to procure
the organs of some potential donors when they perceive that doing so could undermine
the relationship of trust they have with their families (Touraine 2017). These inconsistencies
between law and practice create policy indetermination which precludes a proper policy
governance analysis based on policy knowledge: participants may be simultaneously
right and wrong if they believe that families hold a responsibility in organ procurement
decision-making.
As a matter of fact, our survey attempted to address this topic by including two questions
that explored participants' beliefs about the role given to families when the deceased
had expressed a preference, and when they had not (see Supplementary File, survey
Questions 6 and 7). However, the team decided that ambiguity about policy implementation
in this respect recommended to leave these results out from our policy governance
model, as they were difficult to interpret and any conclusion on family decision-making
would be misleading. More tailored research on family involvement as part of policy
governance quality assessments seems warranted, which should take into account the
law/practice inconsistencies we have identified. Although we cannot address in depth
this issue in this manuscript, we agree with Reviewer 1 (and with Reviewer 2) that
the role played by the next of kin deserves further recognition in our paper.
We have introduced a clarification on the role families play at the beginning of the
discussion section:
(Page 20)
→ Indeed, individual’s explicit refusal to donate, however it is expressed, will likely
be respected in both opt-in and opt-out countries (following national and international
laws and ethical guidelines) [REFERENCE ADDED WHO 2010]. Likewise, an explicit consent
to donate will most likely be respected under both opt-in and opt-out policies, (even
though relatives may be allowed to overrule or veto the deceased's decision under
any of those two policies) (REFERENCE ADDED Delgado et al. 2019).”
Additionally, we have acknowledged this limitation of our model. (Discussion section),
(Pages 25-26)
→ “Fifth, our model for governance quality assessment omits the involvement of potential
donors’ families in the decision-making process. Families may in fact determine whether
or not default policies are followed, and the extent to which the autonomy of the
deceased is respected. However, the level of authority given to families in each jurisdiction
(de iure) can be ambiguous, and is often inconsistent with the role they actually
play in practice (de facto) (REFERENCES ADDED Delgado et al 2019; Morla et al.), thus
precluding the use of this dimension in our model of governance quality, which is
based on societal awareness of actual policies”.
Minor
Introduction - the last word in the first paragraph should be "latter".
This has been corrected:
(Page 2)
→ “a novel framework of analysis that focuses on the latter”
Page 22 - there is no such verb as "concept-proves"
This has been corrected:
(Page 21)
→ “This paper tests a model for measuring that moral and political risk based on peoples
...”
Reviewer #2:
This is an interesting study which is very well performed and gives insight in knowledge
and views about consent policies in seven countries. The authors created a novel tool
for analyzing governance quality and illustrates how the strengths and weaknesses
of different policy implementations can be estimated and compared using quantitative
survey data.
I only have a few details I would like to comment on:
1. In this study countries are divided into 'opt-out' or 'opt-in' consent system.
However, this is not always black and white, for example Belgium (opt-out) system
has the possibility to register 'objection' AND 'consent' to donation. The number
of consent registration even doubles the registration of objection. This nuance is
relevant for the 'limitations of the study' section.
Reviewer 2’s suggestion has made us realize the need to further clarify the difference
between opt-in and opt-out. We do so at the beginning of the Discussion section (p.21),
where we mention that some systems may also allow individuals to express both a consent
and a refusal. We also insert a reference (Rosenblum et al 2012), where this is explicitly
acknowledged:
(Page 20)
→ “Each system allows individuals to express their donation preferences –either to
consent or to refuse organ procurement, or both (see Rosenblum et al. 2012)– by registering
their decision, by holding an organ donor/non-donor card, by writing down advanced
directives, or by communicating their preferences to their family members. In most
cases, the expressed wishes of the deceased (in favor or against donation) are respected,
regardless of the consent system. Indeed, individuals’ explicit refusal to donate,
however it is expressed, will likely be respected in both opt-in and opt-out countries
(following national and international laws and ethical guidelines, such as WHO 2010).
Likewise, an explicit consent to donate will most likely be respected under both opt-in
and opt-out policies, (although relatives may be allowed to overrule or veto the deceased's
decision under any of those two policies) (Delgado et al. 2019). Therefore, the real
difference between opt-in and opt-out policies does not rely on the deceased’s decision
–i.e. consent or refusal– but on the default course of action that applies when the
deceased failed to express any decision: organs can be recovered under opt-out policies
and they cannot be recovered under opt-in policies.”
3. A second minor detail is in the Discussion section, which starts with 'Organ transplantation
policy-making...', I think the authors mean 'Organ donation policy-making'.
We agree, and have changed the wording accordingly
(Page 20)
→ “Organ donation policy-making deals with competing interests and values regarding
the common good, individual preferences, and public trust in institutions”
4. On page 24 it says “Importantly, in most countries, the family of the deceased
are allowed to make decisions over OP when the deceased person had not [5].” In practice
donation is always discussed with the family, regardless an opt-out or opt-in system.
Several studies have shown that family sometimes overrules donor preferences.
This comment by Reviewer 2 converges with the comment made by Reviewer 1 on the relevance
of the difference between “soft” and “hard” consent systems. A full response to that
comment is provided above. Reviewer 2 is right: in practice, in most countries, doctors
give families the authority to overrule donors’ preferences (especially when they
express the wish to donate), even though the law in their jurisdiction may not grant
them such responsibility. As mentioned above, including the role of families in our
model of governance quality assessment was beyond our capacity, because the exact
role families play is surrounded by epistemic uncertainty. Notwithstanding, the corrected
version of the manuscript stresses the fact that families may trump the default option,
thus turning a particular consent system ineffective. We have introduced some changes
in the discussion section:
(Page 20)
→ “an explicit consent to donate will most likely be respected under both opt-in
and opt-out policies, (even though relatives may be allowed to overrule or veto the
deceased's decision under any of those two policies) (REFERENCE ADDED Delgado et al.
2019)”.
(Page 25)
→ “Fifth, our model for governance quality assessment omits the involvement of potential
donors’ families in the decision-making process, even though families may in fact
determine whether or not default policies are followed, and the extent to which the
autonomy of the deceased is respected. However, the level of authority given to families
in each jurisdiction (de iure) can be ambiguous, and is often inconsistent with the
role they actually play in practice (de facto) (REFERENCES ADDED Delgado et al 2019;
Morla et al.), thus precluding the use of this dimension in our model of governance,
which is based on societal awareness of actual policies.”
Reviewer #3:
The statistical analysis approach and software appear reasonable for this research.
However there are concerns with the sample and the general presentation of the results.
1. The investigators claim to have a sample of 2006. Why is there a high percentage
of females?
This question converges with one observation made by Reviewer 1. Both reviewers are
right to warn us of the possibility that our sample may be gender biased. We provide
a twofold explanation for the significantly higher proportion of women than men in
our sample.
First, we have checked that in the Universities and in the study programs where we
recruited the participants there is already a greater proportion of female students.
We have also checked that these numbers mirror actual gender distribution in European
tertiary studies, as reported by Eurostat (the reference is included in the text).
Second, we suggest that the still high percentage of female students in our sample
can be attributed to an answer bias that has also been detected in other studies (we
provide two references where a similar effect has been identified).
To give more prominence to this potential limitation in our study, we have introduced
changes in the Methods section (p12), and in the Discussion (p25).
(Page 12)
→ “Overall, 2006 Austrian, Belgian, Danish, German, Greek, Slovenian and Spanish students
(age bracket (mode) = 20 to 24 years) took part in our study. A majority of them (74%)
were women (see Table 1), which partially reflects an overrepresentation of women
in the disciplines concerned [Supplementary file] (REFERENCE ADDED Eurostat), but
may also account for an answer bias, as mentioned in the Discussion section”.
(Page 25)
→ “Second, our sample shows a gender bias across all countries and study fields. The
fact that more women took part in the survey than did men can be partially explained
by high female-to-male ratios in the sampling frame (supplementary file) –particularly
among majors in health sciences (54-72%; vs 39-62% for humanities/social sciences)–
as well as in the European student population (72% for health sciences students; 64%
for humanities/arts/social sciences students; see [REFERENCE ADDED EUROSTAT, 2018]).
Controlling for the gender distribution in the population, we still observe some overrepresentation
of women in our sample, which may stem from sex differences in non-response bias,
previously detected in other studies [19, REFERENCE ADDED Damman et al] indicating
a higher retention and completion rates among women than men.”
What is the general size of the population from which the sample is drawn and how
representative is this sample of the population and in particular of the opt in and
opt out countries as well as the disciplines being sampled?
In the revised version of our manuscript (Abstract, Introduction, and Methods sections),
we clarify that our study employed convenience sampling methods (see pages 1, 5 and
11). Neither our recruitment methods, nor the demographic sections of our study, were
designed in order to ascertain the representativeness of the samples. As such, we
now de-emphasize the precise values we obtained for each country, and focus on evaluating
the strengths and limitations of our proposed model.
Additionally, throughout the paper, we now emphasize the non-representative nature
of our study samples (Introduction, page 6).
(Pages 5-6)
→ “Our sample (N = 2006) serves the purpose of testing the theoretical framework,
but the respondent population is highly selective and cannot be considered representative
of national populations, as discussed below”.
In the Limitations section (p.27) we also acknowledge the importance of generalizing
these findings to nationally representative samples throughout Europe in order to
better establish the governance quality across several countries, considering the
general population as a whole.
(Page 26)
→ “Future work should use nationally representative population data to conduct the
same governance analysis”.
What statistical plan was in place to determine that 2006 was, in fact, the sample
needed for this survey?
We established a target sample size per country of 200 participants –which we met
and exceeded at every site except for Slovenia and Greece. According to sensitivity
power analyses, this target sample size provided sufficient statistical power to detect
small effects in our main analyses of interest (i.e., knowledge and attitudes; see
Methods section, p14).
We set the 𝛼 level to .05 and power (1 - 𝛽) to .80 and conducted power analyses for
one-sample proportion (knowledge rates) and t-tests (support/opposition attitudes).
A target sample size of 200 participants per country (mean n per country = 287) provided
sufficient statistical power to reliably detect small effects (Cohen’s g = .10, Cohen’s
d = 0.20) in each separate country. This information has been included as a new paragraph
in the Methods section, page 14.
(Pages 13-14)
→ “To evaluate whether our sample size afforded adequate statistical power to examine
variation in knowledge and attitudes across countries, we conducted sensitivity power
analyses for one-sample proportion tests (i.e., knowledge) and t-tests (i.e., attitudes).
Setting the alpha-level to .05 and power (1 - beta) to .80, a per-country target sample
size of 200 (mean n/country = 287) enabled our study to reliably detect small effects
on knowledge (Cohen’s g = .10) and attitudes (Cohen’s d = 0.20) in each country. In
turn, our aggregate sample size (N = 2006) provided almost perfect power (> 99%; alpha
= .05) to detect small effects even in multivariate analyses (i.e., f2 = .02).”
2. What bias checks were made of the sample to assume its validity in this context?
The validity of the sample and methods was checked as follows:
With regard to the instrument’s content validity, we conducted several peer review
rounds prior to administering the survey, first among the researchers involved, then
seeking help from external colleagues in different countries. We then translated the
questionnaire from English to each countries’ language, and then we back translated
it to English to ensure accuracy. Finally, we used the resulting questionnaire to
conduct pilot tests with lay people in two countries –Germany and Spain–, followed
by interviews with the respondents.
With regard to the validity of the sample (a population integrated by university students
overrepresented by women who was surveyed about public policies on organ donation),
we have analyzed whether students’ knowledge and attitudes typically differ from the
rest of the population with regard to organ donation, and whether women typically
differ from men with regard to this topic.
To address these two questions, we have analyzed results from previous surveys on
knowledge and attitudes toward organ donation policies. Two systematic reviews identified,
respectively, 13 studies before January 2008 (Rithalia et al. 2009) and 60 studies
from 2008 to 2018 (Molina-Pérez et al. 2019). In addition, we also checked the European
Commission’s Special Eurobarometers n° 272 on organ donation (2007), n° 333a on organ
donation and transplantation (2010), and n° 426 on blood, cell, and tissue donation
(2015).
The Special Eurobarometers (SE) show no significant difference by age or gender among
Europeans on awareness of organ donation laws (SE 2010), willingness to donate their
own organs after death or organs from a deceased close family member (SE 2007, 2010),
and no difference by age on willingness to donate tissues after death (SE 2015). However,
all three studies indicate that education level was a socio-demographic discriminator:
people educated till age 20 or later were more likely to be aware of the law and to
support organ or tissue donation after death. This is relevant for our governance
quality assessment model, which takes policy awareness as one of its main variables.
The new version of the manuscript acknowledges this in the Limitations section (p.
26, see below).
The Eurobarometers’ results are consistent with nationally representative studies
conducted in Germany, Spain, England, Denmark, Slovenia and Greece. In Germany, Decker
and colleagues (2008) found that men and women did not differ regarding possession
of an organ donor card. While women were more generally willing to donate organs after
death than men, the difference was less than 3% (women 62.1% v. men 59.2%). No significant
gender differences were found in the attitudes toward the different forms of consent
legislation. In Spain, Conesa and colleagues (2003) found no gender effect on attitudes
toward organ donation but some effect of age and education, with younger (<35 yo)
and higher educated respondents (high school, university) being more favorable than
older (>50 yo) and lesser educated respondents. In a more recent Spanish study, Scandroglio
and colleagues (2011) found that “the disposition towards donation varies as a function
of the level of social insertion, reflecting a common result in the literature, in
which reticence is associated with a lower socio-economic or cultural level and more
advanced ages”. In England, Webb and colleagues (2015) did not find significant differences
by age or gender on overall willingness to donate, although there were differences
when considering specifics (willingness to donate all organs or only some of them).
In Denmark, Nordfalk and colleagues (2016) found that younger people were most strongly
in favor of organ donation and also strongly opposed to a presumed consent system,
but this study did not specify how much different the students’ attitudes were in
relation to the average willingness to donate (85%). In Slovenia, Berzelak and colleagues
(2019) reported that the donation willingness tends to increase with education (although
the effect only reaches significance when comparing the lowest and highest educated
respondents) and was significantly higher among women than men, with no significant
effect of age (except for older respondents). In Greece, studies on students (Symvoulakis
et al. 2014; Katsary et al. 2015) report higher levels of law awareness than a study
on patients attending Greek general practices in a rural and urban setting (Symvoulakis
et al. 2013). However, the Greek law changed from opt-in to opt-out between the patients’
study and the students’ studies, making it difficult to assess how much of the difference
in their responses can be attributed to the sampling.
In general, it is difficult to assess how much students' responses in a given country
vary from the general population because, as pointed out by our previous systematic
review (Molina-Pérez et al. 2019), most general public surveys have been conducted
in opt-in countries (and most are not peer reviewed scientific papers but grey literature
funded by governments or national transplant organizations), while most surveys on
students have been conducted in opt-out countries.
Conversely, there are some indications that students’ knowledge and attitudes towards
organ donation, while different, are not at odds with the general population. In Germany,
we conducted a students survey at the University of Göttingen in 2008/09 and again
in 2014/15 (Schicktanz et al. 2017) whose results are consistent with the only available
representative German survey conducted by the Federal Centre for Health Education
(BzgA) also in 2008 and 2014. In Spain, a study on medical students—carried out in
2010-11—reported a willingness to donate of 80% (Ríos et al. 2019), which is approximately
15% above the level reported in the general public in Spain (Scandroglio et al. 2011;
Conesa et al. 2005). More recently, we conducted a representative study in Spain's
Andalusia region that shows no significant effect or only limited effect of age, education,
and gender on knowledge and attitudes toward organ donation policies (Díaz-Cobacho
et al., submitted for publication).
In sum, based on the analysis of these studies, it can be inferred that, overall,
women’s knowledge and attitudes do not typically differ from men with regard to organ
donation, and that students have higher awareness of organ donation policies than
non students.
Moreover, since the aim of our study is to compare countries among each other, we
believe that the presence of a sampling bias does not necessarily affect the validity
of the study as long as this bias is present across countries.
The new version of the manuscript accounts for these validity checks as follows:
(Page 24)
→ “This study has some limitations. First, the surveyed sample was drawn from the
university student population, which is overrepresented by women, and highly non-representative
of the general population of key variables such as age, educational attainment, and
socioeconomic status. Reassuringly, however, previous studies on knowledge and attitudes
toward organ donation policies in Europe show no significant effects of age or gender
on awareness of organ donation laws (REFERENCE ADDED Special Eurobarometer 2010),
willingness to donate their own organs after death or organs from a deceased close
family member (REFERENCE ADDED Special Eurobarometer 2007, 2010), and no age differences
in willingness to donate tissues after death (Special Eurobarometer 2015). Still,
education level has been found to predict donation-related attitudes: enrollment in
tertiary studies is associated with greater awareness of the law and support for posthumous
organ or tissue donation. (REFERENCES ADDED Special Eurobarometer 2007, 2010, 2015).
Therefore, we can expect that nationally representative studies would show lower levels
of policy awareness, resulting in lower national scores in policy governance quality
assessments. / “However, the education bias can be seen as less problematic for our
approach as we were interested in the relation of attitudes and knowledge, and less
on absolute knowledge levels. Since the aim of our study is to compare countries among
each other, the presence of a sampling bias does not necessarily affect the validity
of the study as long as this bias is present across countries.”
Regarding sampling bias, we have clarified in the current version that our study was
conducted on a convenience sample. In addition, we checked the gender bias in our
sample. The higher presence of women aligns with the greater proportion of women in
the sampling frame (i.e., the study programs from which we recruited our sample),
and also in the university student population in Europe. The other potential bias
that we have considered is the non-response bias. It is difficult to identify whether
the reasons why some students decided not to participate in the study are relevant
factors for the purpose of the study.
The new version of the manuscript emphasizes these limitations as follows:
(Introduction, Page 5-6)
→ “Our sample (n=2006) serves the purpose of testing the theoretical framework, but
the respondent population is highly selective and cannot be considered representative
of national populations, as discussed below”.
(Methods, Page 12)
→ “Overall, 2006 Austrian, Belgian, Danish, German, Greek, Slovenian and Spanish students
(age bracket (mode) = 20 to 24 years) took part in our study. A majority of them (74%)
were women (see Table 1), which partially reflects an overrepresentation of women
in the disciplines concerned [Supplementary file] [REFERENCE ADDED EUROSTAT], but
may also account for an answer bias, as mentioned in the Discussion section”.
(Pages 25)
→ “Second, our sample shows a gender bias across all countries and study fields.
The fact that more women took part in the survey than did men can be partially explained
by high female-to-male ratios in the sampling frame (supplementary file) –particularly
among majors in health sciences (54-72%; vs 39-62% for humanities/social sciences)–
as well as in the European student population (72% for health sciences students; 64%
for humanities/arts/social sciences students; see [REFERENCE ADDED EUROSTAT, 2018]).
Controlling for the gender distribution in the population, we still observe some overrepresentation
of women in our sample, which may stem from sex differences in non-response bias,
previously detected in other studies [19, Damman et al] indicating a higher retention
and completion rates among women than men.”
(Page 27)
→Third, in comparison to other surveys about organ donation [20], the present questionnaire
was longer and more time-consuming, so this can also select for highly motivated participants.
This reason may account for some students’ decision not to participate in the study.
3. The investigators use p-values in general. However, they use terms or expressions
such as ‘preponderance’ and ‘tendency to support’. What is the quantitative setting
for these terms?
We describe statistical significance above the midpoint as ‘tendency to support’,
and statistical significance below the midpoint as ‘tendency to oppose’. This applies
to both the one-sample proportion tests, and the one-sample t-tests. We have clarified
this on pages 15 and 17
(Page 14)
→ “Our first analysis step includes a test of participants’ attitudes toward a basic
premise of the SHC concept, namely, the preference for public involvement in policy
decisions. To assess this question, we conducted a series of one sample t-tests against
the point of neutrality (μ = 3.5)”.
(Pages. 16)
→ “we sought to understand whether countries differ in the extent to which participants
favor the policy in place in their own country. For instance, support (/opposition)
among German students would be defined by their favorable (/unfavorable) attitudes
toward the opt-in system, whereas support (/opposition) among Spanish students would
be defined by their favorable (/unfavorable) attitudes toward the opt-out system.
We then conducted a series of one-sample t-tests against the point of neutrality (𝜇
= 3.5),. interpreting significant differences between national means and the scale
midpoint as either a tendency to support the policy in place (if the national mean
exceeds the midpoint), or a tendency to oppose the policy in place (if the national
mean falls below the midpoint).”
Supporting information file (ADDED INFORMATION ON SAMPLING FRAME)
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