The Structure of ICF
ICF is a hierarchical classification: a branch of the classification comprises very general categories that include entire domains of functioning down to very detailed descriptions of specific aspects of functioning. As a classification, the data coded at a very granular level is preserved at the broader level as well.
ICF is organised in two parts, each of them comprising two components:
Part 1 - Functioning and Disability, includes
- Body Functions and Structures
- Activities and Participation
Part 2 - Contextual Factors, includes
- Environmental Factors
- Personal Factors (not yet classified in ICF)
Each component is subdivided into domains and categories at varying levels of granularity (up to four levels), each represented by a numeric code.
The prefix of an ICF code is a letter (b, s, d, or e) that represents the component where the code appears: the prefix "d" represents the Activities and Participation component; although, a user, depending on his specific needs, may choose the more granular optional "a" for Activities or p for "Participation".
Following the initial letter, the number of digits that make up the code indicates the category and its level:
- First digit → is used to represent the first-level categories
- Chapters 1-8 → body functions and structures
- Chapters 1-9 → activities and participation
- Chapters 1-5 → environmental factors
- 3 digits → are used for second-level categories
- 4 digits → for the third-level categories
- 5 digits → for fourth-level categories
When selecting the most appropriate category for an specific aspect of functioning, the first step is to allocate the item to the appropriate component, then to the domain and chapter, and finally, within a given block of the chapter, select the category that best describes the aspect of functioning with the required level of detail.
To complete a code a qualifier needs to be present (a minimum of one qualifier must be indicated for each code) → the qualifier is placed after the ICF code, separated by a decimal point or + sign. Qualifiers specify information about functioning status, such as the magnitude, the location, or the nature of a problem:
- The first, common qualifier specifies the extent of the problem, whether it is the impairment of a body function or structure, a limitation in activities, or a restriction in participation. It is also used to convey that there is no functioning problem (qualifier '0'), which constitutes a neutral description of human functioning.
For environmental factors, the first qualifier specifies the extent of a negative effect (e.g. the size of a barrier) or that of a positive effect (e.g. how strong a facilitator factor is); in this latter case, the decimal point after the ICF code is replaced by the + sign.
Values of the generic qualifier of a problem (impairment, limitation, restriction, or barrier), which, as said above are added to the code after the decimal point are shown below. This qualifier uses a five point scale to indicate the presence of an impairment and its degree:
|xxx.0||NO problem||none, absent, negligible||0-4%|
|xxx.1||MILD problem||slight, low||5-24%|
|xxx.2||MODERATE problem||medium, fair||25-49%|
|xxx.3||SEVERE problem||high, extreme||50-95%|
Example of an ICF code with a 'mild' qualifier:
|b2.1||Sensory functions and pain||1st level item|
|b210.1||Seeing functions||2nd level item|
|b2102.1||Quality of vision||3rd level item|
|b21022.1||Contrast sensitivity||4th level item|
The performance qualifier
This qualifier indicates what a person does in his environment; that environment includes the overall societal context, since performance can also be understood as the involvement in a life situation or the "lived experience" of a person in his actual context. The person's environment will include assistive devices or assistance, whenever he uses them to perform actions or tasks.
The capacity qualifier
This qualifier describes a person's ability to execute a task or an action. It indicates the highest probable level of functioning of a person in a given domain at a given moment.
When a person has a capacity problem associated with a health condition that incapacity is part of his state of health. To assess the full ability of a person, a standardized environment is needed to neutralize or account for the varying impact of different environments on the ability of the person. A standardized environment could be: an actual environment commonly used for capacity assessment in test settings; an assumed environment thought to have a uniform impact; or an environment with precisely defined parameters based on extensive scientific research. The capacity construct will then reflect the environment-adjusted ability of the person in a specified domain. The assessment is carried out without assistive device or assistance.
For international comparisons, the environmental adjustments need to be the same; with this purpose, features of that standardized environment can be coded using the Environmental Factor classification.