Towards a universal concept of vulnerability: Broadening the evidence from the elderly to perinatal health using a Delphi approach
Towards a universal concept of vulnerability: Broadening the evidence from the elderly to perinatal health using a Delphi approach
Nynke de GrootID 0 2
Gouke J. Bonsel 0 1 2
Erwin BirnieID 2
Nicole B. Valentine 2
0 Maternity Care Academic Research Group, Department of Obstetrics and Gynecology, University Medical Center Utrecht, Utrecht University , Utrecht , The Netherlands , 2 Department of Obstetrics and Gynecology/ Division of Obstetrics and Prenatal Medicine, Erasmus Medical Center , Rotterdam , The Netherlands
1 Department of Public Health, Erasmus Medical Center , Rotterdam , The Netherlands , 4 Erasmus School of Health Policy and Management, Erasmus University Rotterdam, The Netherlands , 5 Public Health , Environmental and Social Determinants of Health Department (PHE), World Health Organization , Geneva , Switzerland
2 Editor: Baltica Cabieses, Universidad del Desarrollo , CHILE
Data Availability Statement: All relevant data are
within the manuscript and its Supporting
Funding: This study was funded by ZonMw (The
Netherlands Organization for Health Care Research
and Development (grant 50-52000-99 and
RCPSWN grant 50-50200-98-061; https://www.
zonmw.nl/en/). Both grants were awarded to GB.
The funders had no role in study design, data
collection and analysis, decision to publish, or
preparation of the manuscript.
Both panels showed surprising convergence on the pathways of vulnerability to
health/illhealth, and their interaction. The agreed conceptual model describes a dynamic relation
between health and ill-health and vulnerability. The 2 key pathways that link to vulnerability,
are complementary, but not symmetrical as biological processes of maintaining health or
obtaining better health are not reciprocal to recovery, so also not in terms of vulnerability
impacts. An individual?s degree of vulnerability is the net balance of risk effects and
protective and healing factors (socially, biologically and in terms of health literacy and health care
access). These factors can for measurement purposes (according to the panels: interview
Competing interests: The authors have declared
that no competing interests exist.
Abbreviations: RCPSWN, Regional Perinatal
Consortium South-West Netherlands; SGA, Small
for Gestational Age; R, Resource; C, coping; E,
Environment / exposure / etiological factor; M,
Manifestation; SE, Self-efficacy.
for exploration, checklists for population research) be grouped into ?material resources?,
?taking responsibility for one?s own health?, ?risky activities and behaviors?, and ?social support?.
Supportive and transforming action can thus be undertaken.
A universal concept of vulnerability in the context of health was successfully derived after
careful replication and extension of an international Delphi study on vulnerability among the
In the past decade there has been an increased focus on ?vulnerability? in health [
some heterogeneity of definitions and contexts, it is generally accepted that the population?s
health, access to and results from medical care are at the individual and aggregate level strongly
related to vulnerability [
]. Vulnerability, also referred to as social disadvantage or
deprivation (these terms are used interchangeably), is thus closely related to the societal challenge of
health inequalities. While the existing heterogeneity of vulnerability definitions may be
acceptable for the general picture, and advocacy, it is a persistent obstacle for evidence-based action
to address it . Several authors proposed a definition of vulnerability [
] with different views
of vulnerability as either a determinant of ill-health or impeding factor in the process of
recovering from ill-health. Due to this conceptual heterogeneity, research results in this context and
recommendations are difficult to compare, lessons learnt in one clinical area or subpopulation
cannot easily be transferred to another, altogether hampering the creation of an evidence-base.
To our knowledge, the first to converge on an encompassing, global concept of vulnerability
was the Commission on Social Determinants (CSDH) of the World Health Organization
] while working on health care and cross-sectoral recommendations to reduce the
effects of vulnerability. A formal definition, however, was not outlined.
The starting point of this paper was our engagement in a nationwide evidence-driven
reform of perinatal care in the Netherlands, with a focus on the decrease of perinatal health
]. Perinatal health inequalities are reckoned among the most important
inequalities from a public health point of view . Initial differences in perinatal health
influence the remaining life span [
]: suboptimal physical and cognitive development arises
from the two most common adverse outcomes, small for gestational age (SGA) fetuses and
prematurity. Both morbidities universally show strong inequality gaps [
7, 9, 13?14
from intricate genetic-environment (gen-environment) interactions, these inequalities tend to
give rise to adult diseases and to similar health problems in the next generation, creating
pseudo-hereditary effects of vulnerability and deprivation .
We observed, like other researchers of the elderly and the mentally ill [
], that lack of
vulnerability definitions and measurement tools limits scientific progress in perinatal research
and health service practices (e.g. uniform antenatal check at booking visit, and report of
inequalities in quality/benchmark documents). Also hindered is coordination with adjacent
fields of social policy to address health inequalities, e.g. youth care and regional and city
programs for the deprived e.g. directed to deprived or vulnerable young mothers.
Our study aim was to develop a universal, encompassing, concept of vulnerability, which
could be applied to perinatal health. To this end, and with consent of the original authors, we
adopted and broadened the approach of a similar study focused on vulnerability in the elderly
and designed a 2-stage Delphi study [
]. Two independent expert-panels from a wide range
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of fields, where vulnerability is a key concept, were involved. In the first stage information was
formally elicited on how these experts understand and translate ?vulnerability? into care
practice, into research concepts, and into measurement approaches. In the second stage it was
tested whether the expressed views could be unified into a single concept, or?in the worst
case?whether such a unification should be rejected. This Delphi procedure was independently
repeated in a special interest group concerned with clinical perinatal health care only. A
unified concept of vulnerability, which extends to perinatal health would improve research on
perinatal health inequalities, and also contribute to the broader challenge of exchanging and
accumulating evidence to address vulnerability and health inequalities in general.
This study uses a two-stage Delphi design [
]; a flowchart of the study design can be
found in Fig 1.
The first stage consisted of conducting two formal literature searches, creating a reader
thereof, and preparing a targeted questionnaire (S1 and S2 Appendices). The questionnaire
contained 7 sets of questions (indicated by ?tasks?), to be used in conjunction with the reader.
The materials were designed to explore the commonality of different vulnerability concepts (if
any), and to explore the potential for an overarching relational scheme.
In the second stage, 2 face-to-face expert meetings were held, involving two entirely
different panels of experts. Panel 1 was the general panel consisting of various clinical and public
health experts. Panel 2 was the specific panel on vulnerability in pregnancy. Sociodemographic
and educational data were collected for descriptive analysis. Panel 1 was offered the reader and
questionnaire in advance; the results were discussed during the expert meeting.
Panel 2 did not receive the reader in advance; and instead we presented the questionnaire
during a member-meeting of the Regional Perinatal Consortium South-West Netherlands
(RCPSWN); every question was preceded by a short oral introduction with abstracted
information from the reader. The RCPSWN aims to improve the system of care for vulnerable
pregnant women within the South-West Netherlands. As such, panel 2 participants were assumed
to be above average informed on perinatal vulnerability allowing for this procedure.
From here on, the interactive Delphi-part of both expert panel meetings was similar.
Individual responses to the tasks during the first part of the meeting were grouped by the research
group and analyzed for consensus or dissenting views; this allowed ex post the face-to-face
comparison of the opinions of the general versus the perinatal panel. The panel results were
presented back to both panels separately, for final judgment. At no time was there any
information exchanged between these group members. This paper synthesizes the unchanged
contents of the agreed panel meeting reports.
Literature extraction for the reader sent to panel 1. An extensive literature search was
conducted in Embase May 2014 on the concept of vulnerability and its application in
pregnancy. Because the vulnerability literature is poorly structured, where vulnerability is indicated
by different terms (e.g. ?frailty?, ?disadvantaged?) and content differs according to author (e.g.
emphasis on biological factors, access to health care), a formal approach with predefined key
words (only), as in a comprehensive review, was not applicable.
The ill-structured evidence required the use of Embase, rather than the conventional
databases (PubMed, Medline). Embase covers 98% of PubMed and 100% of MedLine, and beyond
these contains more scientific papers in the multidisciplinary fields.
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Fig 1. Flowchart of the study design for both expert panels and the research team.
Technically, the authors constructed a number of search blocks, each block containing a set
of topic related keywords (S3 Appendix). The blocks were derived from work of the WHO
health equity group [
]. The search block ?pregnancy? was added as a specifier for
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vulnerability in the perinatal context. All journals and papers in Embase were deemed eligible
for inclusion; no restrictions were made based on journal ranking or paper type.
The initial result (general and perinatal combined) yielded 2,462 unique papers.
To be retrieved and read in full (criteria set and selection made by first and second author
independently), a paper had to include a conceptual model of vulnerability OR had to describe
a pathway through which vulnerability (however defined, but measurable/operational) affects
a measurable outcome, either health- OR health care related.
The paper had to report on a study carried out in developed countries, be written in English
or Dutch (the reviewer?s native language) and be available in full text. For the perinatal context,
papers had to report on singleton pregnancies and outcomes were restricted to prematurity
and small-for-gestational-age. These criteria led to the selection of 148 papers that were
retrieved in full. The selection criteria and process were documented. Screening reference lists
of selected papers yielded another 84 papers, bringing the total to 232 papers. A summary of
the literature review and selection of papers is presented in Table 1.
The selected papers were sorted according to their relevance (based on content only; no
international guideline available) and ranked 1 through 4. Rank 1 was assigned to papers that
either included a full theoretical model of vulnerability, or explored causal pathway(s) from
vulnerability to changed health status. Rank 2 was assigned to papers that explored the concept
of vulnerability, but without explicitly mentioning a mechanism or by using a term that loosely
connects to vulnerability (e.g. lack of uptake of preventive services in an underserved
population [which points to a mechanism]). Ranks 3 and 4 were assigned to papers that were either
insufficiently relevant for our purpose (e.g. health care needs of vulnerable clients with cancer)
or which did not include vulnerability information despite its title. The papers rated the most
important, i.e. ranks 1 and 2 (n = 29), were then printed and presented in one reader (for the
list of finally 29 included papers, see S1 Table).
Pen and paper questionnaire (both panels). The selected papers provided the formal
input for the questionnaire, apart from the expert?s pre-existing knowledge. The questionnaire
was divided into 7 parts (?tasks?), each containing 1 or more questions covering, among other,
key elements of vulnerability, existing definitions and conceptual models of vulnerability and
ethical considerations. Table 2 lists the 7 tasks of the pen and paper questionnaire. The
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Panel 1 (general vulnerability)
Panel 2 (perinatal focus)
response mode was variable and suited to the type of question. For this paper the responses to
tasks 2 through 5, reported on by both Panel 1 and 2, are discussed in full since they were most
pertinent to deriving a common concept for vulnerability and an associated uniform
measurement approach for diagnosing vulnerability in routine care.
The first topic to be discussed (task 2), related to the elements or components of
vulnerability. The question listed 29 key elements of vulnerability (for example ?lack of resources? and
?substance abuse? [See S2 Table for full listing]) that were frequently mentioned in the
literature review. Each element was assigned by the research team to one of five, pre-defined
domains according to the type of element (?resources? [R], ?coping? [C], ?exposure/etiological
factor? [E], ?manifestation? [M] and ?self-efficacy? [SE]). The experts were invited to assign a
score of 0, 1 or 2 to each element according to its importance for assessing a client?s degree of
vulnerability during routine care. For each of the 29 elements, a sum score across experts was
then calculated to indicate average importance according to the experts.
The next task (task 3) contained a list of 24 published definitions of vulnerability. To each
definition, a score of 0, 1 or 2 had to be assigned according to how well (2 = best) it matched
the expert?s opinion on vulnerability (for a full list of definitions, see S3 Table). Each expert
was required to use all 3 score options 8 times, on the expert level there were 8 ?best?
definitions, the 8 ?less good? definitions and 8 ?poorest? definitions. The scores were aggregated for
each definition of vulnerability separately (theoretical range: 0?24). Definitions could thus be
The third task (task 4) presented 5 competing conceptual models of vulnerability to
respondents. An important area of disagreement was the focus on vulnerability as a cause of ill health
vs. the focus on vulnerability as impeding factor in the recovery process, once being ill. Panel
members were asked to indicate the model that, according to their opinion, best described the
causal model of vulnerability and health outcomes. Modifications were allowed to the extent
that experts could devise a model of their own. The most frequently selected model was
regarded as preferred option for the panel meeting.
The last topic (task 5) asked for the ?best practice??according to the expert?to assess a
client?s degree of vulnerability under routine health service conditions; this was asked for several
health care domains (mental health care, the elderly, pregnant women, child and youth care,
chronically ill). Panel members were presented?as point of departure?the following options:
1) by checklist (with or without professional support), 2) during an interview or 3) by using
registry data [i.e. medical data]. Other methods could be put forward. Experts were invited to
write down an example of such a ?best practice?, if available. For each domain of health care,
the distribution of assessment preferences was calculated.
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Recruitment and selection. For panel 1, a total of 26 national experts were approached
for participation (no reward). Inclusion criteria for experts (set by the second author) were: 1)
researchers with a proven track record on vulnerability or vulnerability related topics (e.g.
geriatrics [frailty], epidemiology and public health) or clinical specialists with a documented
special interest in vulnerable clients (documented in terms of professional position and/or
scientific contributions), and 2) they had to have a senior position in their respective
organizations (such as head of department/municipal service or associate professor). By selecting
experts from both public health and clinical expertise, we aimed to assure the creation of an
eclectic comprehensive view on vulnerability. Sociodemographic characteristics of panel
members are listed in the middle column of Table 3. Ten experts did not participate in the study
because they felt unable to contribute sufficiently. The 13 experts that agreed to participate
were sent the reader and questionnaire. Ten experts returned their filled-out questionnaires
before the meeting, two handed them in during the meeting. All but one expert were present
during the meeting. Panel 1 meeting took place on November 11th, 2014 at a central location
in The Netherlands (Utrecht). A qualified independent professional chaired the meeting, with
the explicit instruction not to strive for consensus (or dissimilation), but to stick close to the
group result as it emerged. The authors had no role in this process. Detailed notes were made,
subject to the confirmation of all individual experts. The chairman also monitored the time
and assured equal input from all panel members on each topic. With permission of the experts,
the panel meeting was recorded with a voice recorder; the recordings were transcribed
verbatim, and the unaltered verbatim report was sent to all panel members for confirmation. We
allowed for (minimal) changes only for clarification purposes. This amended report was
incorporated into the final data synthesis (available on request); it also enabled the panel members
to check our summarizing statements.
Panel 1 (N = 13)
Panel 2 (N = 68)
Panel 2 consisted of attendees of the RCPSW symposium on vulnerability in pregnancy,
which took place on November 20th, 2014. A total of 68 members were present and agreed to
participate. Sociodemographic characteristics are listed in the right column of Table 3.
During the symposium, each panel member was handed an abridged copy of the
questionnaire containing tasks 2 through 5. After a general introduction by the research team, and
instruction on the schedule of the meeting, each task (2?5) was introduced separately. All
panel members filled out responses individually. The response forms were collected and count
data were analyzed during the break. At the end of the symposium, the initial results could be
presented back to the panel members as a group, for finalization. The feedback provided was
incorporated (see below).
Tasks not presented in this paper. Tasks 1, 6 and 7 of the pen and paper questionnaire
are not presented in this paper. These were completed by panel 1 only, the general research
experts, due to time constraints and, in the case of task 1, due to the requirement of in-depth
theoretical knowledge or research experience. A short explanation of each task was provided
Task 1 invited experts to compare by a Venn diagram technique their definition of
vulnerability with the concepts of self-sufficiency, deprivation, frailty and susceptibility. Task 6
contained open-ended questions on ethical aspects of vulnerability in particular on the
responsibility for its improvement. Task 7 required judgment on four hypothetical
persons/clients. Experts of panel 1 were invited to indicate the degree of vulnerability (not, partially, yes)
and to point out the characteristic(s) to be removed or changed first to lower the degree of
vulnerability. Task 1 data supported preparation work for the meeting, as the information
provided informed the research team of the heterogeneity of terminology among the attendees.
Task 6 and 7 data were not pertinent to this paper.
The duration of panel 1 was about 2 hours, the net duration of panel 2 was about 1 hour. From
a procedural perspective the participants of panel 1 provided about equal input. Panel 2 was
too large to elicit individual comments of all persons being present at all tasks, but discussion
was lively with active involvement of most. Most panel 2 members had previous experience in
discussing these topics on RCPSW meetings. The tasks 2, 3, 4 and 5 (original numbering) are
presented here for both panels simultaneously.
Task 2: Elements of vulnerability
The top 11 elements of vulnerability according to panel are listed in Table 4 (columns 1
through 4; column 5 and 6 describe the position of the elements in the model that is presented
in subsequent section). Although panels differ in their emphasis on specific elements, this
difference seems a matter of terminology: panel 1 primarily uses conceptual terms while panel 2
prefers operational terms (i.e. ?lack of material resources? [conceptual] vs. ?living in a deprived
neighborhood? [operational]). Taking this phenomenon into account, we regarded 4
overarching components as core to vulnerability according to both panels: (1) having insufficient
material resources of various kinds; (2), being and feeling unable to take responsibility for one?s
health; (3) partaking in unhealthy or risky activities and behaviors; and (4) experiencing
inadequate social support.
Task 3: Existing definitions of vulnerability
When the definitions were ranked according to their sum score of preference, the results for
both panels were nearly identical, with 6 generally preferred definitions. The top 6 definitions
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Elements with the equal sum score. R = Resource; C = Coping; E = Environment / exposure / etiological factor; M = Manifestation; SE = Self-efficacy.
of vulnerability are displayed in Table 5. All preferred definitions emphasize the etiological
biological pathway from vulnerability to becoming ill, more than the pathway which
emphasizes the impaired return to a healthy state, if care and self-care are insufficient due to
vulnerability. Panel 1 members commented that no perfect definition of vulnerability exists, but that
they preferred an imperfect yet good compromise above having no definition at all or only
?pure? definitions which are partial. Arguments in favor of a compromise were the wish to aid
policy makers in decision-making regarding resource distribution, the need to increase clinical
acuity among young care professionals for the many ways vulnerability is at work, and the
everyday experienced need to harmonize registries and guidelines to create consistency in
multidisciplinary treatment or care transfers.
The view of panel 1 is represented by 4 statements. First, vulnerability primarily results
from the interaction of the person and his/her environment (social, physical). The degree of
vulnerability is the net result of risk increasing and risk reducing (i.e. protective) factors in this
interaction. Second, this interaction is bidirectional: risk factors may affect the person?s
resilience, and through the person?s inadequacy to respond to challenges, the environmental
supports (protective factors) may be depleted, further increasing the strain on the person.
Third, vulnerability is not a simple summation of risk and protective factors, but more so
the convergent impact of interacting risk factors. A person may be able to withstand a certain
risk or risky situation, but may be unable to continue to do so if another specific stressor is
introduced which, due to its interaction with the other risk factors, disturbs the existing
delicate equilibrium, resulting in the person becoming susceptible to adverse health outcomes:
expert members recalled their experience that in seemingly equal situations of vulnerability
and deprivation, some women experience severe effects, while others do not.
Finally, vulnerability does not only influence the person itself, but also his/her significant
others, such as the partner, family or informal carer, which is part of the above bidirectionality
of the interaction. When explicitly asked to select (mutually blinded) the 2 best definitions out
of the 6 generally preferred definitions, a great majority of panel 1 members (71% of votes)
selected the same 2 definitions that best matched their views. These are presented here as P1-1
and P1-2 respectively, with their source.
Definition P1-1: Vulnerability is a multidimensional construct reflecting a convergence of
many risk factors at both the individual and community levels, which influence health and
healthcare experiences [
Definition P1-2: Vulnerability is the susceptibility to harm resulting from the interaction of
risk factors and supports and resources available to individuals and groups [
In the discussion with panel 2 members?who were usually active caregivers in the
perinatal field?the increased probability of adverse outcome [after health care interaction] received
most attention, more than the nature of reinforcing mechanisms as in panel 1. Consequences
prevailed over mechanisms. After the discussion, this panel too was invited to vote for the 2
best definitions. The majority (63%) selected the following:
Definition P2-1: Frailty [vulnerability] is a dynamic state affecting an individual who
experiences losses in one or more domains of human functioning (physical, [psychological, social),
which is caused by the influence of a range of variables and which increases the risk of adverse
Definition P2-2: Vulnerable populations are groups at increased risk for poor physical,
psychological, and social health outcomes and inadequate health care [
In the discussion, a tentative definition is presented that combines the strengths of the
above definitions and perspectives of both panels, and gives credit to the arguments put
Task 4: Competing models of vulnerability
Both panels had difficulty determining the model that best suited both their preferences on the
elements and the assumed relations among all elements. The underlying difficulty appeared to
be the reflection of the multitude of pathways into one model or scheme. Consequently, none
of the available models was clearly preferred and some experts had circled all or none of the
models. During the discussion, however, an agreed overarching scheme/conceptual model
(Fig 2) could be defined, based on 3 principles.
The first principle was the acknowledgment of the existence of two separate pathways
between vulnerability and health (e.g. adverse outcome, illness): the pathway to adverse
outcomes (pathway to becoming unhealthy) and the pathway of recovery, once being unhealthy
(pathway to healthy). It was recognized that these pathways are not symmetrical in the sense
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Fig 2. Conceptual model of vulnerability for research and practice.
that the risk leading to ill health not necessarily prevents its recovery, and that preventive factors
on the way to an adverse outcome do not necessarily improve an adverse outcome once it occurs.
The figure conveniently does not make a distinction between short and long-term factors.
The second principle was the distinction between biological etiological pathways on the one
hand and care pathways (either preventive, curative or supportive) on the other hand. Care
pathways are determined by the national health system and the public social care structure,
much more so than biological factors. In Fig 2, the upper part reflects the direct etiological
pathways, the lower part the pathways through care mechanisms.
The third principle (see also the result of task 2) was the presence of reinforcing feedback
loops of factors through ill health, which causes vulnerability to create greater and more
persistent adverse effects, than might be expected from the factor in isolation. The figure shows the
most pertinent negative feedback loops; in data analysis these interactions are reflected in
specific forms of epidemiological analysis.
Next, the resulting conceptual model of vulnerability is shown. The term ?pathway? both
refers to a specific process, and, in epidemiological analysis, to a probability that some change
is induced by the factor involved.
Conceptual model of vulnerability. The left side of the model represents the pathway to
adverse outcomes. It encompasses general and individual risk factors and the (lack of) uptake of
specific preventive care services (e.g. lack of uptake of immunizations by specific populations
]). General risks, such as gender, age or living in a deprived neighborhood increase
vulnerability and the susceptibility to adverse outcome, regardless of their interaction with specific risk
factors . Specific risk factors are individual risk factors such as substance use and personal
resources, such as social support, social network and coping skills. These specific risk factors
reinforce one another and their combined effect influences the degree of vulnerability. Taken
together, vulnerability then becomes the net result of general and specific (individual) risk
factors and availability of personal resources, regardless of socio-economic strata.
11 / 17
Moving to the right side of the model, the pathway of recovery represents the process of
recovery given the degree of vulnerability. This process runs through the natural prognosis and
professional and self-care. The natural prognosis is inversely related to vulnerability as the risk
factors that contributed to the occurrence of adverse outcomes are generally still in place (e.g.
recovery rates of smokers vs. non-smokers differ [
]). At the same time, vulnerable
individuals are a challenge in professional care as they require complex and often interdisciplinary case
management  and dropout rates are high [
]. Through associated experiences, vulnerable
individuals subsequently develop the tendency to avoid professional care altogether [
Finally, self-care relies heavily on health literacy, which in turn is strongly related to general
risk factors (i.e. to vulnerability). Estimates of health illiteracy in the general populations vary
from 30?50% [
Task 5: Diagnosing vulnerability in routine care
If invited to choose one preferred method to assess vulnerability in routine situations or
research, the majority of both panels indicated a face-to-face interview as the preferred
method, preferably supported with some training. However, during the discussion both panels
advocated a combined use a checklist and face-to-face interview as most effective and efficient
since the majority of clients or respondents are sufficiently able to fill out a checklist by
themselves, and as a method to decrease interview heterogeneity as training is not always a feasible
option. The care professional thus could use the results from a general checklist as the input
for the face-to-face interview to assess the client?s degree of vulnerability, perhaps tailored to
the context. In words of one of the members from panel 1: ?The checklist leads to a hypothesis,
which is then tested during the interview.? In the case of checklist barriers that cannot be
overcome with support, assessment should rely on thorough face-to-face interviewing only.
A Delphi-like procedure with two independent panels of experts clearly showed shared views
on the definition of vulnerability and its measurement despite their different backgrounds
(general vs. specific). The following shared conceptual definition of vulnerability was agreed
upon: 'Vulnerability is a dynamic state that reflects converging effects of a set of interacting and
amplifying personal and environmental factors, which together increase an individual?s
susceptibility to ill health and which hampers the recovery process to normal health once ill health has
occurred.' More importantly, the process generated an agreed universal model of vulnerability,
which can guide data collection, data analysis, and policy development. The three guiding
principles are: pathways to ill health vs. return pathways to health; division between care
factors vs. biological and social factors; the mechanism of risk accumulation and reinforcing
interaction between person and environment. The agreed model shown in Fig 2 unites
seemingly different views of previous authors into one consistent framework. The recognition that
vulnerability not only initiates disease but also impacts prognosis, and interferes with recovery,
creates opportunities for separate, yet consistent research and care options to decrease
A standard list of measurable components of vulnerability has become available from our
study, which can be grouped into four areas: having insufficient material resources of various
kinds, being and feeling unable to take responsibility for one?s health, partaking in unhealthy
or risky activities and behaviors, and experiencing inadequate social support. Within these
four groupings, convergence on the ?best set? was less marked. It appears that within fields like
care for the elderly, mental health, or perinatal care, particular vulnerability components have
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The main difference between panels was a general preference by panel 1 (foremost
researchers with various backgrounds) for a definition where the interacting and reinforcing
mechanism was explicitly stated, while panel 2 (foremost caregivers) preferred at least full
account of the multiplicity of adverse health outcomes (biological, functional and social health
states). We explain this difference in emphasis by the difference of professional focus and not
by a mismatch between the general concept and a ?perinatal? concept of vulnerability.
The presented definition and model are designed with translation to multiple disease areas
and practical application in mind, such as child services, mental health care, care for the
chronically ill, and care for the elderly. The model offers a framework to understand interactions
between types of risk and protective factors; the elements associated with each factor will have
to be determined separately for each domain through e.g. literature research, consensus
amongst experts, and consultation of administrative sources. Also, implementation in the
social care domain can be considered, extending the conventional socio-economic
However, the implementation of the preferred measurement by checklists and subsequent
interviews is not self-evident. At least two barriers may be encountered.
Routine non-research settings such as a social service desk, an ambulatory care unit or a
prenatal screening unit will consider the cost of information collection in terms of acquisition
time and information technology, versus the direct gains from a ?better? or more consistent
measurement of vulnerability. Gains are considered not only for the client but also the
organization. To some extent this perception of ?cost? depends on the current awareness of many
insufficiencies and inefficiencies in the care for the vulnerable or deprived. If health
inequalities are unnoticed, uncommon, or, have low priority, systematic vulnerability measurement
will meet resistance. An argument in favor is that at least in perinatal care, the systematic
approach ultimately seems time-saving [
], and we observe that increasingly the practical
usefulness of checklists for vulnerability is accepted in clinical intake procedures.
Another barrier relates to lack of professional awareness and the feeling of embarrassment
which professionals experience when they face a case of vulnerability. Lack of intervention
options, presence of communication barriers, and the expectation that adequate care is time
consuming, all contribute to the reluctance to give full attention to vulnerability-related care
Societal and professional resistance may also be expected with ?too? good a measure of
vulnerability. Systematic measurement inevitably detects more cases of vulnerability and more
adverse, perhaps preventable, consequences. Better measurement induces questions on
responsibilities for the inadequacies observed, which few like to address as no easy solution is
present in view of the intersectoral nature of vulnerability, especially in resource-constrained
settings. Apart from hesitation to measure adequately, societal resistance is reflected in
changing views on the degree to which vulnerability concerns are a personal responsibility, rather
than a society?s responsibility to its members. Each member of Panel 1 addressed his/her
ethical position towards health inequalities and its sources; this view might affect the model. As
was already clear from the choice of elements, consensus was presented on the mechanisms of
vulnerability and the pathways to ill-health and recovery. But, while the majority view
considered health outcome inequalities as undesirable, the extent to which society and the medical
system vs. the individual was responsible for improvement, differed. Generally, the clinical
and public health system were responsible once adverse outcomes are manifest; thus, health
access inequalities were rejected . Different views existed on responsibilities for the
non13 / 17
medical part of the process. The equal-opportunity-for-all principle for most experts involved
active societal efforts to reduce health outcome inequalities also in the social domain. For all,
the model was suitable to reflect various ethical views on vulnerability, in terms of the choice of
the elements, the pathways to be influenced, and the methods of influence.
Despite these caveats, which will require careful attention to information policy, we believe
the population and the clients have a right to know what affects their prospects, as indeed this
is the only way to involve them in solutions. Health care insurers could do their part by
creating arrangements that compensate for the added burden of good care to these clients.
Strengths and limitations
The strength of this study is the generalizability of our model. The mechanisms described are
general and the model incorporates both public health and clinical care elements, all of which
are supported by international papers. The model pertains specifically to health and health
care in developed countries, as the Dutch health care system is similar to other Western
countries. In underdeveloped countries vulnerability is frequently an issue of life and death, thus
the magnitude of the effects can be more severe. However, the studies on so called
?responsiveness? of health systems (WHO term [
]), which combining data from many countries with
quite diverse stages of development, clearly show that the mechanisms through which
vulnerability, education, and welfare act on health are quite universal [
Another strength of our study was the variety of backgrounds of experts. While the
preparatory work to equalize information level was maximized, this did not necessarily imply that all
experts should or would agree. There is a sharp difference between shared concepts, stated in
various terms (scenario 1), and different latent concepts, even when terms superficially suggest
ideas converge (scenario 2).
Scenario 2 could have occurred; if this had been the case, that result would have been
reported. Actually, scenario 1 was the case, and congruence was beyond our expectation in
particular across panels. We never required the experts to converge, while this also was
unlikely to happen having invited esteemed professionals with a view. In the end, scenario 1
was more applicable: the variety of experts indeed turned into a strength of our study,
suggesting the robustness and generalizability or the results. Third, this study made maximum use of
available literature from different views within different domains. During the panel meetings,
apparently different literature views could be reconciled and together with features of different
domains could be incorporated into one general, overarching conceptual model. Fourth, this
study explicitly addressed the practical application of the vulnerability concept in routine care
(i.e. measurement); all elements put forward by members form both panels can be reliably
assessed with a checklist. Even though the use of checklists has its limitations (i.e. socially
desirable answers, impaired literacy or other barrier), using checklists is common practice in
other fields [
] and has also been advocated within pregnancy care [
]. Finally, this study
is repeatable; all study materials are available on request.
A limitation of this study is that there was one, national, generic expert panel, which we
contrasted with only one field-specific group (i.e. perinatal care). The extension to more
contexts (i.e. fields and countries) is welcomed and could induce further refinements or
modifications. Second, the full model and its pathways need to be tested further. To this aim we are
currently introducing a vulnerability checklist in a large, prospective cohort of pregnant
women in the Netherlands, which aims to disentangle the interaction of risk factors and their
convergent impact on adverse outcomes. Finally, filling out a checklist is a cognitively
demanding task, which some individuals might not be able to do (due to for instance, a
language barrier or intellectual disability) or perceive as troublesome. In the former case, where
14 / 17
these barriers cannot be overcome, we recommend vulnerability assessment to rely on a
thorough interview with a trained professional only.
A universal conceptual model of vulnerability, with a proposed measurement approach, has
been developed. The concept can be applied in perinatal services and tested further in research
and practice in multiple disease areas and subpopulations. Uniformity in definition and
concept will benefit researchers, policy makers, care professionals and clients alike. It will facilitate
comparability across research results, across subpopulations for specific care, and allow for
more equitable resource allocation in care. Admittedly, to disentangle the intricate interactions
of reinforcing risk factors and their effect on health and health-related adverse outcomes, and
to develop effective and feasible intervention strategies, more research is needed.
S1 Appendix. Vulnerability questionnaire (original language).
S2 Appendix. Vulnerability questionnaire (English translation).
S3 Appendix. Literature search ?Blocks? for vulnerability used in embase.
S1 Table. Key papers on vulnerability included in the reader that was sent to Panel 1
members prior to the expert meeting.
S2 Table. 29 Elements presented for the common vulnerability concept.
S3 Table. List of 24 Existing vulnerability definitions as included in the written
Our thanks go out to all research and health care professionals involved in the Delphi panels,
and many colleagues.
Special thanks goes out to B.M.C. Akerboom, gynaecologist and perinatologist Albert
Schweitzer Hospital, Dordrecht; H. Burger, associate professor Epidemiology, University
Medical Center Groningen; R.J.J. Gobbens, lecturer and senior researcher ?frailty? in the elderly,
Rotterdam University of Applied Sciences; M.J.B.M. Goumans, director and professor
integrated care for elderly, Research Centre Innovations in Care, Rotterdam University of Applied
Sciences; J. Harting, senior researcher Department of Public Health, Academic Medical Centre
University of Amsterdam; I. de Kruijff, paediatrician, Zuwe Hofpoort Hospital / St. Antonius
Hospital, Woerden; F. van Lenthe, associate professor of Social Epidemiology, Erasmus
Medical Centre Rotterdam; J. Meulmeester, medical doctor ?Veilig Thuis Haaglanden? (Advice
and Reporting Centre for Child Abuse and Domestic Violence), The Hague; G. Smulders,
researcher and epidemiologist ?Monitor Social Vulnerable Populations?, Community Health
Services, Tilburg; H.F. van Stel?, assistant professor Health Services Research, University of
Utrecht; M.A.S. de Wit, senior researcher Public Mental Health Care, Public Health Service,
15 / 17
Amsterdam; A.J.M. Waelput, programme director ?Healthy Pregnancy 4 All, Department of
Obstetrics & Gynecology, Erasmus Medical Centre Rotterdam; and E. van der Zwan, member
of the board of the Centre of Expertise Maternity Care, Hoofddorp, for accepting our
invitation to participate in panel 1. Our thanks also go out to A.N. Rosman, senior researcher
?Pregnancy and employment?make it work!?, Department of Obstetrics & Gynecology, Erasmus
Medical Centre Rotterdam, for acting as independent chairman during the panel 1 expert
Conceptualization: Gouke J. Bonsel.
Formal analysis: Nynke de Groot, Gouke J. Bonsel.
Methodology: Gouke J. Bonsel.
Supervision: Nicole B. Valentine.
Writing ? original draft: Nynke de Groot, Gouke J. Bonsel.
Writing ? review & editing: Nynke de Groot, Erwin Birnie, Nicole B. Valentine.
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