Chapter 4. The WHO's ICF

4.1 Introduction to the ICF

The International Classification of Functioning, Disability and Health, to repeat its full title, has been developed over a number of years by the World Health Organization (WHO) and formally adopted by its General Assembly in 2001. Its aim, as a classification system, is to provide a language and framework for the description of health and health-related states that can be used consistently across different countries and settings. It provides a description of situations with regard to human functioning and its restrictions and serves as a framework to structure this information in a meaningful and easily accessible way.

Such a framework is obviously indispensable if valid comparisons across countries are to be possible, but is also enormously helpful in providing a common framework for use by different data collectors and systems in any one country. Without such an agreed framework within which to set a wide range of information and a standardised common language to describe it, communication across countries and disciplines becomes impossible and one is confined to a fragmented set of non-comparable observations.

The ICF seeks to encompass what a person does do or can do, covering not just body functions and structures but also activities and participation together with environmental and other contextual factors. Functioning and disability are conceived as multi-dimensional concepts relating to body functions and structures of people, the activities they do, the areas of life in which they participate, and the factors in their environment which affect these experiences.

Within the ICF, functioning is an umbrella term encompassing all body functions, activities and participation; disability is then used as an umbrella term for impairments, activity limitations or participation restrictions. Disability is seen as the outcome of a complex relationship between an individual’s health condition, personal factors, and the external factors of the environment in which he or she lives, with the framework specifically designed to capture such environmental factors. The underlying model is one where contextual (environmental and personal) factors interact with the individual with a health condition and determine the level and extent of that individual’s functioning. This the WHO present as an integration of the medical model of disability – which views disability as primarily a problem of the person caused by their health condition – and the social model, which sees disability mainly as socially created, reflecting the nature of the environment in which people live, rather than an attribute of the individual. The ICF, according to WHO, attempts to achieve a synthesis between these two with a “biopsychosocial” approach incorporating the biological, individual and social perspectives on health.

The term ‘disability’ in the new ICF is thus defined as follows:

“an umbrella term for impairments, activity limitations and participation restrictions. It denotes the negative aspects of the interaction between an individual (with a health condition) and that individual’s contextual factors (environmental and personal factors).” (WHO 2001 :213)

Central to this definition of disability is the relationship between the individual (with a health condition) and environmental factors (physical, social and attitudinal). It is the interaction of the person’s health characteristics and their contextual factors (environment, personal) that produces disability. If a person with a given health condition lives in an environment characterised by barriers at every level their performance will be restricted; but if a person lives in a facilitating environment this will serve to increase their performance.

The ICF in this respect represents a significant development from the previous classification system employed by the WHO called the International Classification of Impairments, Disabilities and Handicaps (or ICIDH). In that earlier framework, the focus was on classification of the limitations in people’s activities as a consequence of an impairment (see for example Bickenbach et al 1999). While the influence of social and environmental factors was recognised at the conceptual level, in practice the ICIDH did not provide any way to capture the effect that an unaccommodating environment has on people’s lives. Impairments and their severity could be recorded, but no more. For this reason, the ICIDH came to be regarded as fundamentally flawed by those advocating the social model of disability, including many organisations representing people with disability. The ICF in many respects developed out of responses to that fundamental critique.

In meeting that critique, the ICF shifts the focus from body dysfunction classified as impairments to the three dimensions of impairment, activity and participation. Participation is covered broadly to include key areas of everyday life. The inclusion of an additional component on environmental factors then aims to ensure that the context in which people are actually operating and the barriers they face can be incorporated. The ICF is by design a classification of human functioning on a continuum, applying to people across the age ranges and in different countries; it applies to anyone, whatever their health status, rather than being a classification of people with disabilities – it adopts a universalist perspective in that sense. While not without its problems at conceptual and operation levels – as we shall see shortly – the ICF is very widely regarded as a major improvement on what was previously available. It has been accepted as such by a wide range of organisations representing people with disabilities, which had a substantial input into the development process.

4.2 The ICF in More Detail

Table 1 first sets out the general framework of the ICF. This divides into two parts, Part 1 dealing with Functioning and Disability while Part 2 covers Contextual Factors. We now look at each of these in more detail, in order to clarify what the ICF involves in practice.

Part 1 of the ICF, Functioning and Disability, has two components:

  • Body functions and structures, and
  • Activities and Participation.

Body Functions are the physiological functions of body systems, and would include for example seeing, hearing, feeling pain, remembering. (Mental or psychological functions are subsumed under body functions). Body Structures are anatomical parts of the body, for example the eye, the mouth, the spinal cord. Impairments are then defined as problems in body function or structure such as significant deviation or loss, for example loss of vision or limbs. The ICF thus first provides a structure within which information on the presence and severity of an impairment in relation to a specific body function or structure can be recorded.

Turning to Activities and Participation, an activity is defined as the execution of a task or action by an individual, while participation is defined as involvement in a life situation. Activity limitations are then difficulties an individual may have in executing a particular task or action, while participation restrictions are problems he or she may have with involvement in a particular life situation. A set of nine domains is distinguished, as shown in Table 2, for recording activities and participation across different areas of life. Getting around inside or outside the home would come under the mobility domain, for example, washing and dressing oneself would come under self care, and employment would come under the “major life areas” domain, and religious observance would come under community, social and civic life.

Table 2: Domains for Activities and Participation


Learning and applying knowledge
General tasks and demands
Self-careDomestic lifeInterpersonal interactions and relationships
Major life areas
Community, social and civic life

In relation to each of these domains, information can be recorded on both performance and capacity. Performance relates to what a person does in the area in question, in the environmental context in which they actually live. Capacity, on the other hand, refers to their ability to execute a task or action if the environment were uniform or standard – for example, the environment commonly used for capacity assessment in test settings. The gap between capacity and performance is then intended to reflect the difference between the impact of the actual versus uniform environment. In relation to both performance and capacity, information on whether this is with and without assistive devices or personal assistance can also be recorded.

Part 2 of the ICF then covers Contextual Factors. At the conceptual level, these are divided into

  • Environmental factors and
  • Personal factors.

Environmental factors comprise the physical, social and attitudinal environment in which people live, and which are external to the individual. They include at individual level the physical features of the environment that the person faces, the communication devices they have available, and the support networks they have from family, friends etc. on a day-to-day basis. They also include at a societal level the formal and informal structures, services and systems in place, such as state agencies, transport and communication services, education and training, laws and regulations, and attitudes.

Disability is seen as the outcome of a complex relationship between an individual’s health condition, the external factors of their environment, and personal factors. Personal factors are features of the individual that are not part of a health condition or state – including for example gender, race, age, lifestyle, social background, education, occupation, and psychological characteristics. Such personal factors are not actually coded in the ICF framework itself, but are included in the conceptual model which underpins it.

4.3 Using the ICF

The ICF consists of a set of codes, into which information from different sources – such as surveys or clinical observation – can be transformed. These first of all show which dimension the information relates to, in other words whether it is:

Body functions denoted by the letter “b”;

Body structures denoted by the letter “s”;

Activities and Participation denoted by the letter “d”,

or Environmental factors denoted by the letter “e”.

That element in the code is followed by a digit which distinguishes a number of different high-level categories or “chapters” within each dimension. For both body functions and body structures, the first digit distinguishes 8 chapters and these are shown in Table 3.

Body Functions

Body Structures

The eye, ear and related structures

Skin and related structures

Within Activities and Participation, the 9 chapters distinguished are the domains already set out in Table 2 above. Within Environmental Factors,five categories are distinguished, namely

  1. Products and technology
  2. Natural environment and human changes to it
  3. Support and relationships
  4. Attitudes
  5. Services, systems and policies.

Having identified the high-level category or chapter with the first digit of the code, either one or three more digits can be used to distinguish further sub-categories within each. The concise version of the ICF employs just two levels, while the full version offers a more detailed categorisation and employs four. The full version is presented as a useful for specialist services such as rehabilitation, whereas the concise version may suffice for surveys or clinical outcome evaluation.

The ICF codes then have the crucial component, namely what are termed qualifiers, which indicates for example the presence and severity of a problem. The WHO emphasise that without the presence of these qualifiers, the codes have no inherent meaning, and so any code should be accompanied by at least one qualifier. The first qualifier employs a common 5-point scale applying across body functions and structures, activities and participation, and environmental factors as follows:


Table 3: ICF High-level Categories Distinguished Within Body Functions and Body Structures

Structures involved in voice and speech

No problem
1Mild problem
2Moderate problem
3Severe problem
4Complete Problem

(The value “8” is used to indicate “not specified” and “9” to indicate “not applicable”).

In relation to body functions and body structures, the first two chapters, having a problem means an impairment and the first qualifier indicates the severity of that impairment. In relation to activities and participation, the first qualifier refers to limitations or restrictions. In relation to environmental factors, the first qualifier denotes either the extent of facilitators or positive effects of the environment or the extent of negative effects or barriers; these are distinguished by putting a “+” in front of the qualifier to indicate facilitators and a “-” to indicate barriers.

To illustrate how the coding framework is actually used, then, some examples may be helpful. The code


indicates that in relation to body functions there is a severe impairment in specific mental functions of language. The code


indicates in relation to body structures that there is a moderate impairment of the upper extremity. The code


indicates in relation to activity and participation that there is a mild difficulty in bathing. The code


indicates that there is a total barrier to accessing education.

Further qualifiers may then be employed, in the body structures and activities and participation dimensions only. In the case of body structures, a set of additional qualifiers indicates whether the change in structure is total, partial, qualitative etc. In the case of activities and participation, the additional element indicates whether the problem or limitation is present when assistive devices are not used.


4.4 Some Conceptual and Practical Problems in Using the ICF

Although a significant development on what was previously available, the ICF is not without its conceptual problems. For example, the distinction between “Activity” and “Participation” proved problematic. As the framework was being developed, Activity was thought of as relating to the person level and Participation to the social or societal level. (This corresponded in a general way to the “disability” versus “handicap” dimensions in the ICIDH). However, it became clear that a consensus could not be reached on which domains should be categorized under Activity and which should be included under Participation: what some conceived as a personal activity others saw as social participation. The approach adopted by WHO to break this deadlock was to declare all domains both personal and social, and leave it up to users whether to regard something as Activity, Participation or both. The distinction between person and society levels underpins much of the empirical literature on disability, but WHO has in effect taken the position that this distinction is unnecessary, potentially confusing and optional at best (see Hendershot 2001).

This has left a rather unsatisfactory situation where there is considerable overlap between Activities and Participation, and a lack of clarity about when a particular observation is to be entered under one or both. Some ICF users have preferred to try to designate each domain as either Activity or Participation, but this has run up against the same problem faced by WHO. It might be possible to arrive at a broad consensus about categorising some of the domains – “learning and applying knowledge”, “general tasks and demands”, and “self care” as Activities, for example, and “interpersonal interactions and relationships”, “major life areas” and “community, social and civic life” as Participation. However, it seems that “communication”, “mobility” and “domestic life” are particularly difficult to categorise as one or the other. In Australia and Canada, for example, several options for splitting the domains have been suggested but bodies such as the Canadian Institute for Health Information and the Australian Institute of Health and Welfare have not been able to recommend a particular split.

Another significant area of contention in the development of the ICF has been the distinction between “Performance” and “Capacity”. Performance relates to what a person does, in their actual environmental context, with or without the use of personal assistance or special equipment, whereas Capacity refers to their ability to execute a task or action in a “standardized” environment. It is not at all clear however what a uniform or standard environment means in specific instances, much less how survey questions could reliably assess activity in relation to such an environment. In fact, it might in many cases be more productive to think of capacity in terms of an optimum rather than standardized environment: from an intervention perspective, the spotlight is then on how the actual environment could be brought closer to that optimum. The notion of a uniform or standardised environment on the other hand seems to come from the disciplinary perspective of medical or psychological testing in a controlled environment.

Approaches to tackling the practical problems created by these conceptual difficulties are being advanced as the ICF is being employed across a variety of countries and settings. The WHO position is that in this early phase of ICF implementation, users will wish to experiment with various approaches, and testing, recording and sharing of experience among them will be an essential element in its evolution. This still leaves the user with some hard choices and significant uncertainty.

Those leading the implementation of the ICF in Australia, where it is particularly advanced, see three main ways in which the ICF can be applied to disability data collection (ICF Australian User Guide Version 0.5):

  1. as a framework to aid in the selection and organisation of areas to include at the design stage, ensuring that information of interest is not omitted.
  2. as a set of classifications that can be used as a ‘menu’ from which to choose the domains of interest. Decisions need to be made regarding the level at which the classifications will be used – for instance at chapter level (e.g. mobility), at block level (‘walking and moving’), using the second level category (‘walking’), or third level category (‘walking short distances’).
  3. to provide qualifiers that assist the researcher to choose a scale that is either directly related to an ICF qualifier or that ensures that the data collected will be mapped to an ICF qualifier.

It must be emphasised that no one survey could possibly hope to provide comprehensive information across all the areas which are in principle encompassed within the ICF: any application must have a distinct focus, which will determine the appropriate balance across areas and topics. The ICF is a general coding system, not a questionnaire. It is extremely detailed and it would not be possible to classify functioning in terms of all of the sub-categories of functioning, activity and participation. Choices have to be made as to what elements, and in what level of detail, to include in an actual instrument. These choices need to be informed by policy considerations (what will the information be used for) as well as by practical considerations (how much information is it reasonable to request from a respondent; how much information can the collecting agency afford to gather).

Some of the choices to be made include:

  • Whether to emphasise the recording of detailed information at the level of impairment, activity or participation.
  • How much of the projects resources to commit to developing items in areas that are new to the ICF and that are not available in existing instruments

The decision on which elements of the ICF to emphasise needs to be informed by an understanding of what the information will be used for. Planning of health services, for instance, requires detailed information at the level of the impairment: its causes, the body structures affected, its severity and nature. Planning of support services for people with disabilities would be more likely to take the level of impairment as a given and to focus on what people need in order to facilitate participation in activities generally, with less regard to causes. Clearly, both type of policy and both types of information are needed, but in drafting a questionnaire choices need to be made regarding the balance between them.

Another major challenge facing would-be users of the ICF in a survey context is that survey methodologies are much more advanced in some dimensions than others. Many of the components of a disability survey are well-developed in that instruments based on the older ICIDH can be drawn on when it comes to classifications of impairments – although one may have to choose between a wide range of alternative formulations. However, reflecting the ICF’s emphasis on participation and on environmental factors as mediators poses particular challenges in terms of survey design. There has been much less development and testing of instruments designed to include the dimensions of participation and environmental elements in a systematic fashion (Me and Mbgoni, 2001). There is some scope to learn from the experience of others, but in an ICF context that is rather limited so far [1]. On the other hand, this makes lessons learned from its application in Ireland particularly interesting.

Consultation with key stakeholders is obviously crucial in deciding which elements of the ICF to emphasise, since people with disabilities are uniquely qualified to assess which aspects are most salient. A structured consultation process was a core element in the current project, and we proceed in the next section to describe that process and its findings.

  1. Hendershot (2001), in a review of international instruments and recommendations for instruments, dealing with disability, notes that the domains of 'general tasks and demands', 'domestic life' and 'community, social and civic life' are rarely covered in these recommendations and the instruments based on them.