In this section, we discuss as to what degree the current ICF framework, the definitions, and the classification may capture the core features in the reports on work disability (see Table
3).
Table 3
Core features in disability evaluation and their coverage in the ICF
1) Functional capacity of the claimant | Activity and participation | Activity and participation | |
2 Health condition (Disease, symptoms, complaints) | Health condition Body functions/structures | (∅) Body functions/ structure | Disease is a component of the ICF framework but not included in the ICF definitions. It can be coded in the ICD*. |
3) Socio-medical history (claimant's development and severity of ill health condition, his previous efforts to regain health and return to work, job and social career) | Implicit in the framework but no explicit presentation | ∅ | The ICF definitions do not cover the development over time. |
4) Prognosis of disease and functional capacity | ∅ | Partly: capacity | The ICF framework and ICF definitions do not cover the time perspective. |
5) Feasibility of interventions and rehabilitation | Environmental factors | Environmental factors (facilitators and barriers) | The ICF framework and ICF definitions cover intervention and rehabilitation however; they do not cover dynamic time perspective or the qualification ‘requirement to comply’. |
6) Causality: functional incapacity exclusively caused by health condition | ∅ | ∅ | The ICF framework displays a person holistically |
7) Consistency of the situation of the claimant | Partly: between the impairments, activity limitations and restrictions in work | ∅ | |
8) Ability to work (in general hours and %) | ∅ | ∅ | |
The framework
The ICF framework describes disability as a composite concept that integrates impairments, activity limitations, and participation restrictions with personal and environmental factors. As such, the framework is well suited to present work disability as a particular manifestation of disability. In general, the ICF framework dwells on the interaction of the health condition with the functioning of the individual (rather than on aetiology or disease) [
40]. It also visualizes the relevance of environmental and personal factors on all components [
23]. Professional guidance to insurance physicians from an increasing number of countries keeps stressing the importance of the benefits of the framework and discourages a traditional biomedical approach that simplifies disability as a specific state of health [
20,
21,
41].
Disability is a process rather than a state. Disability refers to the past, present, and future outcome of a person’s interaction with his/her physical, social, cultural and legislative environment [
17]. The ICF framework does not address this process aspect explicitly. The personal factors include aspects of the past (such as education) but in a static way. We are unable to describe the dynamic development of health and health-related domains, nor are there means to express the future events and prognosis of work [
38]. With capacity, we can indicate the expected performance in a standardized environment but are still missing the dynamic development. This is a significant limitation of the ICF framework.
In several countries such as such as France [
42], Germany [
21], the Netherlands [
41], and Switzerland [
20] restricting the causal relation between the health condition and activities is explicitly requested in order to recognise legal work disability. Limitation of activities resulting from lack of motivation, or lack of participation resulting from unemployment does not count. The ICF framework distinguishes the domains and their interaction but does not foresee a restricted causal relation. The guidance of disability evaluation in these countries encourages the insurance physicians to first draw a holistic picture of the claimant, compatible with the framework and to then discount the non-medical factors from the overall judgement of disability. It is unclear how the ICF framework can capture these aspects of disability evaluation.
The definitions
As stated above, the ICF classification contains 1122 explicit definitions (not including body structures or personal factors). The definitions can serve to standardize and harmonise the evaluation reports, and avoid ambiguity and variation in the presentation and interpretation of the findings. Our question is if the ICF definitions capture the core features of disability evaluation.
The core features functional capacity, health state, and the ability to participate in working life can be described with the components ‘body structure/function’ and ‘activity and participation’. As the ICF has not been specifically developed for work disability, it stands to be tested if the present set of definitions is comprehensive in this field.
Aspects of the socio-medical history and prognosis can be depicted with the definitions, but it is not practicable to line up the content in a chronological sequence. Like the framework, the definitions, do not describe the dynamic development of disability. Therefore, socio-medical history, and prognosis are not easily covered in the ICF definitions.
Interventions can be described as facilitating environmental factors. In disability evaluation, we need to qualify some interventions as feasible. Such qualifiers do not exist currently, which stresses the need to develop them within the ICF concept of environmental factors.
Further, disability evaluation gives a judgment on the claimant's situation. This can be given from two different viewpoints: the (self-) perception of the claimant and the perception of the medical expert. Medical experts usually integrate both perceptions in their reports. Applying the ICF would make it necessary to keep the two systematically apart. Although it is no difficult to separate the two and it can be considered beneficial to do so, it is not a common practice.
Restricting the cause why a person is not able to work is an important statement in disability evaluation. The ICF definitions cannot describe causal relation because the current ICF definitions cannot be put together.
Finally, medical examiners must also provide a general statement about work ability. Percentage, degree of disability or in working hours cannot be described with ICF definitions
The classification
The classification organises categories and definitions in a hierarchical system. The applicability of the classification goes as far as the application of the definitions goes. The refined coding system of the ICF classification can be useful in research, or for documentation, or in the statistics of a social insurance administration. For these purposes core sets have been published in the field of disability evaluation as well. These core sets facilitate the description of functional capacity [
16,
43]. For the other core features different core sets could be developed.
Overall, we feel that using the ICF for development of disability evaluation does hold promises but it also has its limitations. The ICF framework fits modern thinking about disability evaluation. It helps medical experts to describe work disability as a bio-psycho-social phenomenon rather than as biomedical phenomenon only. The framework illustrates the connections between the different components in the disability evaluation that the medical expert has to address. The ICF definitions for body functions, structures, activity and participation, and environmental factors cover essential parts of the disability evaluation. Empirical testing is needed to establish if the definitions are useful and sufficiently detailed. Clear and broadly accepted definitions will support the understanding of the medical reports for professionals and administration and allow the development of instruments.
The ICF framework and definitions are limited in the following aspects: the dynamism of development of disability, definitions for personal factors and, causality and consistency. An explicit time dimension could supplement the present ICF framework. Describing “history and prognosis” in words may overcome the lack of dynamic time perspective. For feasibility of interventions qualifiers could be developed.
Empirical research would be needed to test our considerations in practice. Several studies are underway. In one study, we are testing the consensus-based 20-item core set for functional capacity suggested by the European Union of Medicine in Assurance and Social Security (EUMASS) [
16] for applicability and usefulness across several European social insurance systems.
In another study, Kirschneck et al. translated concepts of disability evaluation to ICF categories by linking medical reports from claimants with low back pain and chronic widespread pain and compared them with the existing core set of these conditions [
13]. The preliminary results of the study show consistency between the pre-existing core sets and the medical reports in Germany [
44].
In a third study, we tested the potential of applicability the ICF core sets of low back pain and chronic pain in disability evaluation in Switzerland [
45]. We studied 72 medical reports from claimants with low back pain/chronic widespread pain and linked those to the ICF categories.
In a fourth study, Linden et al. have tested an ICF-based instrument to assess functional incapacity in patients with mental health problems [
46]. The instrument probes on 13 items of the ICF-component ‘activity and participation’ that are commonly affected in patients with mental disease (e.g. endurance or self-assertiveness).