Biomedical Engineering Reference
In-Depth Information
Health (ICF; WHO 2011) as the basic conceptual model. Their work emphasized the fact
that the ICF model has established the need for a common language that not only allows
a common understanding and use by operators belonging to different professional areas
but is also easily applicable to remarkably different environmental contexts, “resolving the
apparent tension between respecting cultural and linguistic differences in the meaning of
health and providing the scientific basis for an international common language of health”
(Üstün et al. 2001a, p. ix; see also Üstün et al. 2001b, 2003b, 2003c).
The real problem encountered by the experts was, paradoxically, the complex definition
of disability (Üstün et al. 2003a). In fact, in the ICF disability arises out of activity limita-
tions and restrictions on participation that is determined by the interaction between body
function and structure impairments and a disadvantageous context (environmental and
personal factors):
Since only one or two of these dimensions of disability are reflected in measures in any
given survey […], the data will only capture a portion of the population—those who
exhibit the specific aspects of disability the questions represent. (Altman and Gulley
2009, p. 544)
In a complex model such as this, each domain represents a different area of measurement
and each category or element of classification within each domain represents a different
area of operationalization of the broader domain concept. To generate a meaningful general
prevalence measure, one must determine which component best reflects the information
needed to address the purpose of the data collection (Mont 2007, p. 4).
The “definitional paradox” (Madans and Altman 2006) about the definition of disability
is due to the operational nature of the disability concept according to which any theoretical
definition implies aporia, whereas any operational meaning is determined by the pur-
pose of the research. Indeed, the outcome of the interaction between a person's state of
health and contextual factors, the sum of personal and environmental components, can
be described on three levels: (1) body, as impairment of body functions or structures; (2)
person, as activity limitations measured as capacity; and (3) society, as participation restric-
tions measured as performance. For each of these levels it is possible to identify more than
one “operational” definition of functioning and disability: In fact, the ICF does not provide
a single, unequivocal, operational definition and, consequently, does not point to specific
measurement tools. The main consequence is that different operational definitions lead to
different and sometimes incoherent assessments:
Specifically, we are concerned with the similarities and differences in the populations
identified as disabled when the conceptualization of disability, the resulting questions,
and the methods used to code and analyze the data differ from one set of questions to
the next. In addition, we are concerned with disability prevalence estimates when the
same sets of questions are asked in two different national populations. (Altman and
Gulley 2009, p. 544)
Therefore, there are many different aspects for which the operational measures
of disability may vary according to the prevalent notion of disability; the purpose
of measurement and application; the characteristic of disability investigated; and
“the definitions, question design, reporting sources, data collection methods, and
expectations of functioning” (WHO and World Bank 2011, p. 21). Moreover, all of these
factors make comparisons of data at national and international levels very difficult. In
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