New approaches to understanding the impact of musculoskeletal conditions

Best Practice & Research Clinical Rheumatology Vol. 18, No. 2, pp. 141–154, 2004 doi:10.1016/j.berh.2004.02.003 available online at http://www.sciencedirect.com

3 New approaches to understanding the impact of musculoskeletal conditions Alarcos Cieza

PhD, MPH

ICF Research Branch of the WHO CC FIC (DIMDI), IMBK—Department of Physical Medicine and Rehabilitation, Ludwig-Maximilians-University, Munich, Germany

Gerold Stucki*

MD, MS

Professor and Chairman Department of Physical Medicine and Rehabilitation, Ludwig-Maximilians-University, 81377 Munich, Germany

The approval of the new international classification of functioning, disability and health (ICF; formerly ICIDH) (WHO, 2001a) by the World Health Assembly (WHA) in May 2001 is a landmark event for medicine and society. With the ICF, patients’ functioning, with its components body functions and structures, activities and participation, became a central perspective in medicine. The objective of this paper is to outline how the ICF can serve as a new global language of functioning and health and hence become a new approach for our understanding of the impact of musculoskeletal conditions. Key words: mesh: rheumatoid arthritis (RA); musculoskeletal diseases; outcome assessment; quality of life; non-mesh: ICF; ICF core set.

The approval of the new international classification of functioning, disability and health (ICF; formerly ICIDH)1 by the World Health Assembly (WHA) in May 2001 is a landmark event for medicine and society. With the ICF, patients’ functioning, with its components body functions and structures, activities and participation, became a central perspective in medicine. Patients’ functioning is now seen as being associated with, and not merely a consequence of a health condition.2 Additionally, functioning and health are now seen in relation to health conditions and also to personal and environmental factors. Different from the approach of health-related quality of life, which has its focus on patient-reported outcomes, all aspects of the patient experience including activities and participation and also body functions and structures, as well as personal and environmental factors are covered. This bio-psycho-social view is not new to a number of fields in medicine, e.g. rehabilitation and prevention. What is new is that we now have * Corresponding author. Tel.: þ49-89-7095-4050; Fax: þ49-89-7095-8836. E-mail address: [email protected] (G. Stucki). 1521-6942/$ - see front matter Q 2004 Elsevier Ltd. All rights reserved.

142 A. Cieza and G. Stucki

a globally agreed on an etiologically neutral framework and a classification both on the individual and population levels. It, therefore, comes as no surprise that health scientists and rehabilitation professionals in clinical practice, research, teaching and administration, especially in the field of musculoskeletal health conditions, were among the first to recognize the potential of the ICF to improve clinical practice and health services provision, to better disseminate health policy and management and to stimulate research with the common goal of optimizing participation from both the patient and the societal perspective.2 Patient organizations and their advocates are also recognizing the potential of the ICF to generally strengthen the patient perspective in medicine and health systems. Most importantly, the ICF is not only a language for health professionals but for patients also. Indeed, the ICF is a language of potential interest to all of us, since during a life time virtually every one of us will develop a health condition: not only diseases but disorders, injuries or traumas and other ailments such as stress, ageing and congenital anomaly. In line with this view, the ICF overcomes the distinction between the healthy and the disabled. Instead, functioning is seen along a continuum relevant to all people at some point in life. All member states of the WHO are now called upon to implement the ICF into a number of sectors that include, besides health, education, insurance, labor, health and disability policy and health statistics. To implement the ICF into medicine and other fields, practical tools need to be developed. Considering the length of the classification with more than 1400 categories, the main challenge is feasibility. Other challenges include the operationalization and quantification of ICF categories and the linkage of existing measures (including clinical tests and health status measures) to the ICF categories. Most importantly, ICF-based tools need to be tailored to the needs of prospective users without forgoing the information required for health statistics and health reporting regarding the burden of disease. To address the issue of feasibility regarding the number of categories to be assessed and the user’s perspective in medicine, which typically takes a health condition and/or setting perspective, the ICF Core Set project was initiated in 2001. The ICF Core Set project was a joint project of the ICF Research Branch of the WHO Collaboration Center of the Family of International Classifications (DIMDI) at the Ludwig-Maximilians University in Munich, Germany, together with the Classification, Assessment and Surveys (CAS) Team at WHO and an increasing number of partner organizations. The objective of this paper is to outline how the ICF can serve as a new global language of function and health and hence become a new approach for our understanding of the impact of musculoskeletal conditions. The specific aims are to (1) introduce the ICF, (2) introduce the ICF Sets for RA, (3) demonstrate how the ICF can be used to compare the content of health status measures using the example of OA, (4) demonstrate how the ICF and the ICF Core Sets can be used in clinical practice, and (5) discuss future applications of the ICF and ICF Sets for MSC in clinical practice, education, research, health statistics and regulation.

THE INTERNATIONAL CLASSIFICATION OF FUNCTIONING DISABILITY AND HEALTH OR ICF The ICF, as a classification, provides the means to map the different constructs and domains to describe the process of functioning and disability. Accordingly, the ICF contains lists of so-called ICF categories organized in three different components:

Understanding the impact of musculoskeletal conditions 143

(1) Body Functions and Structures, (2) Activities and Participation, and (3) Environmental Factors. Body Functions (b), Body Structures (s) and Activities and Participation (d) belong to the part Functioning and Disability. Environmental factors belong to the part Contextual Factors. Personal Factors, which constitute the fourth component of the classification and also belong to the part Contextual Factors, have not yet been classified. The ICF categories represent the units of the ICF classification. Within the hierarchical code system of the ICF classification, the ICF categories are designated by the letters b, s, d and e, followed by a numeric code starting with the chapter number (one digit), followed by the second level (two digits) and the third and fourth levels (one digit each). Thus, within each chapter, there are individual two-, three- or four-level categories.3 The understanding of the interactions between the components of the ICF is shown in Figure 1. A health condition is an umbrella term for disease, disorder, injury or trauma and may also include other conditions, such as ageing, stress, congenital anomaly, or genetic predisposition. It may also include information about pathogeneses and/or etiology. There are (possible) interactions with all components of functioning: body functions and structures, activity and participation. Body functions are defined as the physiological functions of body systems, including psychological functions. Body structures are the anatomical parts of the body, such as organs, limbs and their components. Abnormalities of function, as well as abnormalities of structure, are referred to as impairments, which are defined as a significant deviation or loss (e.g. deformity) of structures (e.g. joints) or/and functions [e.g. reduced range of motion (ROM), muscle weakness, pain and fatigue]. Activity is the execution of a task or action by an individual and represents the individual perspective of functioning. Participation refers to the involvement of an individual in a life situation and represents the societal perspective of functioning. Difficulties at an activity level are referred to as activity limitation (e.g. limitations in mobility such as walking, climbing steps, grasping or carrying). Problems an individual may experience in his/her involvement in life situations are denoted as participation restriction (e.g. restrictions in community life, recreation and leisure, but may be in walking too, if walking is an aspect of participation in terms of life situation). The contextual factors represent the complete background of an individual’s life and living situation. Within the contextual factors, the environmental factors make up Health condition (disorder or disease)

Body functions and structures

Activities

Environmental factors

Participation

Personal factors

Figure 1. The current framework of functioning and disability—the WHO International Classification of Functioning, Disability and Health (ICF).

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the physical, social and attitudinal environment in which people live and conduct their lives. These factors are external to individuals and can have a positive or negative influence, i.e. they can represent a facilitator or a barrier for the individual. Personal factors are the particular background of an individual’s life and living situation and comprise features that are not part of a health condition, i.e. gender, age, race, fitness, life-style, habits and social background. Risk factors could thus be described by both personal factors (e.g. lifestyle, genetic kit) and environmental factors (e.g. architectural barriers, living and work conditions). Risk factors are not only associated with the onset, but interact with the disabling process at each stage. Within this context, functioning is an umbrella term for body functions, body structures, activities and participation. Functioning denotes the positive aspects of the interaction between an individual (with a health condition) and the contextual factors of this individual. Disability is an umbrella term for impairments at the body level, activity limitations and participation restrictions. Disability denotes the negative aspects of the interaction between an individual (with a health condition) and the contextual factors of this individual.

ICF CORE SETS FOR MSC While it is likely that the ICF framework (see Figure 1) will become the universal for functioning, disability and health it is unclear at this point whether the classification will be adopted as well. Among several factors, the success of the classification will depend on its usefulness and feasibility. As mentioned above, the main challenge in the clinical context is the length of the classification with over 1400 categories. To address this challenge so-called ICF Sets have been jointly developed by the ICF Research Branch of the German WHO collaborating center for the family of classifications (DIMDI) in Munich and the Classification, Assessment and Surveys (CAS) team at WHO in cooperation with a number of international societies including EULAR, the Bone and Joint Decade and the EU health monitor project. In a first project, ICF Sets have been developed for the 12 most burdensome chronic conditions including the musculoskeletal health conditions LBP, OA, OP and RA. In this project, the development of ICF Sets is in line with the current concept in outcomes and quality-of-life research of condition-specific measures3, i.e. it is based on the assumption that different conditions are associated with different spectrums of abilities that are typically limited and represents an attempt to link the use of the ICF with the International Classification of Diseases (ICD-10). Therefore, the ICF Sets represent a link between specific conditions or diseases and relevant ICF categories. Since the requirements to describe functioning in association with a condition are different for a comprehensive multidisciplinary assessment and a clinical study, an ICF Comprehensive Set as well as an ICF Core Set is required.4 The ICF Comprehensive Set for a specific condition is a list of ICF categories that includes as few categories as possible to be practical, but as many as necessary to be sufficiently comprehensive in describing the prototypical spectrum of limitations of functioning and health in a comprehensive, multidisciplinary assessment. The ICF Comprehensive Sets may guide the clinician when examining and taking the patient’s history and may also be of help when deciding and evaluating rehabilitation interventions.2

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Instead, the ICF Core Set for a specific condition includes a list of ICF categories with as few categories as possible to be practical, but as many as necessary to be sufficiently comprehensive in describing the prototypical spectrum of limitations of functioning and health in clinical studies. Whilst an ICF Comprehensive Set should include all abilities that are typically limited in patients with a condition, the ICF Core Set aims to include only the most important ICF categories across cultures and countries to be practical in any situation or setting. The development of the ICF Sets for chronic conditions involved a formal decisionmaking and consensus process integrating evidence gathered from preliminary studies including Delphi exercises, systematic reviews and an empiric data collection, using the ICF checklist.5 The ICF Sets for LBP, OA, OP and RA have been published elsewhere.6 – 9 The ICF Sets are exemplified here with the components body functions and activities and participation of the ICF Comprehensive Set for RA, which are presented in Tables 1 and 2, respectively. The ICF categories in bold represent the categories selected for the ICF Core Set in the corresponding components. The ICF Sets for LBP, OA, OP and RA, as well as all other developed ICF Sets, are preliminary and need to be tested extensively in the coming years in differing countries and regions, in different subsets of patients with varying patient and condition characteristics, in different health care settings and from the perspective of the different Table 1. International classification of functioning, Disability and Health (ICF)—categories of the component ‘body functions’ included in the ICF Comprehensive Set for RA. ICF code

ICF category title

b130 b134 b152 b180 b1801 b280 b2800 b2801 b28010 b28013 b28014 b28015 b28016 b430 b455 b510 b640 b710 b7102 b715 b730 b740 b770 b780 b7800

Energy and drive functions Sleep functions Emotional functions Experience of self and time functions Body image Sensation of pain Generalized pain Pain in body part Pain in head and neck Pain in back Pain in upper limb Pain in lower limb Pain in joints Haematological system functions Exercise tolerance functions Ingestion functions Sexual functions Mobility of joint functions Mobility of joints generalized Stability of joint functions Muscle power functions Muscle endurance functions Gait pattern functions Sensations related to muscles and movement functions Sensation of muscle stiffness

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Table 2. International Classification of Functioning, Disability and Health (ICF)—categories of the component ‘activities and participation’ included in the ICF Comprehensive Set for RA. ICF code

ICF category title

d170 d230 d360 d410 d415 d430 d440 d445 d449 d450 d455 d460 d465 d470 d475 d510 d520 d530 d540 d550 d560 d570 d620 d630 d640 d660 d760 d770 d850 d859 d910 d920

Writing Carrying out daily routine Using communication devices and techniques Changing basic body position Maintaining a body position Lifting and carrying objects Fine hand use Hand and arm use Carrying, moving and handling objects, other specified and unspecified Walking Moving around Moving around in different locations Moving around using equipment Using transportation Driving Washing oneself Caring for body parts Toileting Dressing Eating Drinking Looking after one‘s health Acquisition of goods and services Preparing meals Doing housework Assisting others Family relationships Intimate relationships Remunerative employment Work and employment, other specified and unspecified Community life Recreation and leisure

professions involved in the care of patients. Despite the fact that patient perspective has been addressed in the empirical data collection of preliminary studies, the ICF Sets will need to undergo a close examination and possibly modification by patient focus groups throughout the world. After testing, which will be coordinated by the ICF Research Branch in Munich under the auspices of the CAS Team at WHO and in close collaboration with a number of international organisations, the ICF Sets will finally be approved by an international panel based on a review of the test results. How to link musculoskeletal health status measures to the ICF Many studies compare the psychometric properties of health-status measures, but content comparisons are scarcely represented in the literature. This is probably due to the varying use of concepts, scales and items in the different health-status measures.

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The ICF as a universal framework of functioning and health enables the content comparison of health status measures. The results of such a comparison provide information on which contents are covered by which measure. Thus, the use of the ICF as a reference tool for comparison can provide clinicians and researchers with new insights when selecting health-status measures for clinical studies.10 The first question when selecting health-status measures is to decide on what should be measured based on the study endpoints, the population to be studied, and the intervention. The ensuing question regarding how to measure or which measure to use may be answered based on the content comparison of the possible candidate measures. When planning a study with patients with OA two probable candidate measures are the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC)11 – 13 and the Lequesne-Algofunctional Index.14 – 17 These may be the most recommended and most frequently used outcome measures for OA of the hip and knee in clinical trials.18 The WOMAC and the Lequesne-Algofunctional Index were linked to the ICF separately by two trained health professionals18 on the basis of 10 linking rules which enable health-status measures to be linked to the ICF in a specific and precise manner.19 On the basis of these linking rules, if one item encompasses different constructs, the information in each construct should be linked. For example, in item 1B of the Lequesne-Algofunctional Index ‘morning stiffness or regressive pain after rising’ the concepts ‘morning stiffness’ and ‘pain after rising’ have been linked to the ICF. Consensus between health professionals is used to decide which ICF category should be linked to each item/concept of the two questionnaires. To resolve disagreements between the two health professionals concerning the selected categories, a third person trained in the linking rules is consulted. The results of the linking process of the WOMAC and Lequesne-Algofunctional Index are shown in Table 3. As can be seen in Table 3, it is possible to study the differences as well as the commonalities of health-status measures regarding their representation of body functions, activities, participations and environmental factors. In relation to the linking of health-status measures to the ICF, one could also take advantage of the ICF Sets described above. Adding a determined ICF Core Set to the comparison, e.g. the ICF Core Set for OA, it would be possible to examine whether and to what extent the compared measures cover the prototypical spectrum of problems encountered in patients with OA as defined by the ICF Core Set. Without being in competition with other health status measures, the ICF Core Sets can be the basis for the definition of what should be measured. The content comparison of health status measures based on the ICF can then facilitate the definition of how to measure or which measure to use. How to use the ICF and ICF Core Sets in clinical practice The ICF framework is increasingly used in clinical practice to structure patient problems20 – 22, particularly in multidisciplinary care and for rehabilitation purposes. Physicians and health professionals can use the ICF framework and the ICF Core Sets to identify and document patients’ complaints when taking a patient’s history and to identify and document clinical findings of a clinical examination. The ICF Core Sets may be particularly useful for trainees and may also be of value in the hands of experienced clinicians since physicians could underestimate patients’ functional problems.22

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Table 3. Items of the WOMAC and the Lequesne-Algofunctional index and their corresponding ICF categories. WOMAC items

ICF-code

Body functions 3. Pain at night while in bed 1.-5. Arthritis pain

b134 Sleep functions b28016 Pain in joints

b289 Sensation of pain, other specified and unspecified b7603 Supportive functions of arm or leg 6. Stiffness after first wakng in the morning 7. Stiffness after sitting, lying or resting > later in the day

b7800 Sensation of muscle stiffness or b7808 Sensations related to muscles and movement functions, other specified

Lequesne items

1A-E: Pain or discomfort… 1B: Morning stiffness or regressive pain after rising 1A-E: Pain or discomfort...

3D: Pain or discomfort while getting up from sitting without the help of arms

1B: Morning stiffness or regressive pain after rising

Activities and participation d4100 Lying down

10. Rising from sitting 17. Rising from bed

d4103 Sitting

12. Bending to floor

d4105 Bending

4. pain sitting or lying

d4150 Maintaining a lying position

1B: Morning stiffness or regressive pain after rising 3C(hip): Squat or bend on the knees 1E(knee):Pain or discomfort while getting up from sitting without the help of arms 3A(hip): Put on socks by bending forward 3C(Hip): Squat or bend on the knees 1A: Pain or discomfort during nocturnal bedrest

d4153 Maintaining a sitting position

1E(hip): Pain or discomfort with prolonged sitting (2 h)

d4154 Maintaining a standing position d4400 Picking up

1C: Pain or discomfort after standing for 30 minutes 3B(hip): Pick up an object from the floor 1A: Pain or discomfort during nocturnal bedrest only on movement or in certain positions

d4101 Squatting

7. Stiffness after sitting, lying or resting later in the day 19. Lying in bed 4. Pain sitting or lying 7. stiffness after sitting, lying or resting later in the day 21. Sitting 5. Pain standing upright 11. Standing

d4102 Transferring oneself while lying

1. Pain walking on a flat surface

d450 Walking

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Table 3 (continued) WOMAC items

ICF-code

Lequesne items

d4500 Walking short distances

2. Maximum distance walked (may walk with pain): 1 km (in about 15 minutes) from 500 to 900 m (in about 8–15 minutes) from 300 to 500 m. from 100– 300 m less than 100 m 2. Maximum distance walked (may walk with pain): unlimited 3D(knee): Able to walk on uneven ground 3A(knee): climb up a 1 flight of stairs 3B(knee): climb down 1 flight of stairs

13. Walking on flat surface

d4501 Walking long distances

2. Pain going up or down stairs 8. Descending stairs

d4502 Walking on different surfaces d4551 Climbing

9. Ascending stairs

14. Getting in/out of car 20. Getting in/out of bath 22. Getting on/off toilet 16. Putting on socks/stockings 18. Taking off socks/stockings 15. Going shopping 23. Heavy domestic duties 24. Light domestic duties 7. How severe is your stiffness after sitting, lying or resting later in the day? Environmental factors

d4559 Moving around unspecified d498 Mobility, other specified d5101 Washing whole body d530 Toileting d5402 Putting on footwear d5403 Taking off footwear d6200 Shopping d699 Domestic life, unspecified d9208 Recreation and leisure, other specified e1201 Assistive products and technology for personal indoor and outdoor mobility

1D: Pain or discomfort while ambulating 3D(hip): Can get into and out of a car

3A(hip): Put on socks by bending forward

2. Maximum distance walked (may walk with pain):…with one walking stick or crutch

The use of an ICF sheet21 based on the ICF framework either on paper or in an electronic form is a most useful way to understand the relation between selected target problems and impaired body functions and structures and psychosocial and the environmental factors which exacerbate or help to minimize them (Figure 2). The use of an ICF sheet and the ICF Core Sets can be used to improve internal reporting and documentation and to structure multidisciplinary care.2,23

Health professional perspective

Medical diagnosis: Chronic polyarthritis [ICD: M 05.9] Reactive depression [ICD: F 32.9]

Primary goal of rehabilitation: Maintenance/Improvement of mobility in order to achieve functional independence at home Maintenance of employment

Pain both hips and in both arms

Can t stand and walk for longer periods (e.g. shopping) due to pain

Can·t go to her dancing club anymore

Movement in hips and fingers

Swelling in finger joints

Can t lift heavy objects Dressing: putting on and taking off

Has difficulties with ironing, hanging the clothes up, cleaning, shopping and cooking At work: problems working with the computer

Writing and tipping Body-structure/Function Limitation of movement in upper extremities and hip joints b7101 Instability of hands b7151 Generalized muscle weakness b730

Activity Walking long distances d4501 Lifting and carrying objects d430 Maintaining a body position d415 Changing body position Fine hand use d440 Putting clothes on d5400 Taking clothes off d5401 Using communication devices d3601

Participation Recreation and leisure d9200 Doing housework d640 Remunerative employment d850

Structure of hands 730 and of hip joints s75001 2 Context factors Environmental: Lives in a first floor flat; no elevator e1552; needs aids for hand use e115 Supportive husband and children Personal : Motivated

Figure 2. Illustration of how the ICF components can be used to structure patient problems (listed in the upper section ‘patient perspective’) as well as findings, and observations by the rehabilitation team (listed in the lower section ‘health professional perspective’). Lines between the selected target problems from the patient perspective (circled in the upper section) and impaired body functions and structures as well as the given personal and environmental factors (circled in the lower section) denote their hypothesized relationship. Please note that the wording denotes patients words or special medical terms and not text from ICF categories.

150 A. Cieza and G. Stucki

Name: Mrs. Andrew Age: 54

Understanding the impact of musculoskeletal conditions 151

THE FUTURE OF THE ICF IN CLINICAL PRACTICE, EDUCATION, RESEARCH, HEALTH STATISTICS AND REGULATION For the first time in the history of medicine there is now a universally agreed conceptual framework and classification for functioning, disability and health. The ongoing adoption of the ICF by clinicians and health professionals, researchers, health authorities, health care providers and insurers is likely to trigger a number of important developments.2 Any language influences the way people think. Since the ICF now includes contextual factors, which interact with the components body functions and structures, activity and participation it is likely that people who work with the ICF will increasingly consider these factors and interactions. Also, the now neutral terms body functions and structures, activity and participation as compared to the prior ‘negative’ terms—impairment, disability and handicap—may stimulate a more positive view and bring a more resourceoriented perspective into medicine. The ICF as common language for functioning is likely to change multi-professional communication. As illustrated under the section ‘ICF in clinical practice’, the ICF will become the basis for multi-professional patient assessment, goal setting, intervention management and evaluation. Since rehabilitation is part of the continuum of care from acute to community care, the ICF seems to be a new meaningful way in communicating across the continuum e.g. when transferring a patient. The ICF may also improve communication between patients and health professionals. It will be easier for patients to understand their functioning and health, rehabilitation goals and an intervention plan based on a language they and their proxies can understand. Similarly, the ICF will become an important part for the education of rehabilitation doctors and nurses, physical, occupational and speech therapists, psychologists, social workers and other rehabilitation professionals. Indeed, the ICF is already part of a number of curriculums for physicians and health professionals worldwide. The ICF is already having an important impact on rehabilitation and outcomes. Currently we are faced with ‘competing’ instruments in many areas.20 The mapping of items to the ICF10,18,19 provides a unique opportunity to standardize items and instruments. The results of these studies show, that with a few exceptions, the content of generic- and condition-specific health status measures is represented by the ICF categories and therefore the ICF can serve as a common framework when comparing health status instruments. The components of the ICF are the basis for research into their interactions and will lead to a better understanding of functioning, disability and health.24 Most importantly, the components are a practical framework for designing longitudinal prognostic studies on the negative and positive factors related to functioning and health in persons with a specific health condition or within a specific context. Finally, the ICF will be used by health agencies, health care providers and insurances in many ways. It will, for example, be used for expert opinion or as a framework to develop expert systems, case-management, health reporting and health statistics, quality assurance and benchmarking, health care planning and case management. The ICF may also be used for the development of prospective payment systems. In all these situations a mass of information must be handled and analyzed. Redundant data collection must be avoided and decisions need to be made based on relevant data. The ICF provides a framework for data collection24,25 and a terminology for comparable data25 or for all aspects encompassing functioning. The research community or regulatory agencies may use the ICF and ICF Core Sets to define what should be measured when reporting a clinical study or when defining

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the minimal requirements to be met for approval. In rheumatology, the ICF Core Sets can complement current rheumatological Core Sets.26 Rheumatological Core Sets typically include the domains inflammation as measured by an acute phase reactant and destruction as measured by an X-ray score. The rheumatological Core Set domains pain or vitality as measured by a patient-administered scale can be linked easily to their respective ICF categories. Nevertheless, it is not clear what is exactly meant with the rheumatological Core Set domain ‘function’. Currently, the issue of what is being meant by function is approached by selecting a measure and not by defining the relevant categories to measure the construct ‘function’ Alternatively, the rheumatological Core Set domain ‘function’ could be defined by selecting the relevant ICF categories, an approach which has been taken in the ICF Core Set project. To first define what categories should be covered when referring to the rheumatological domain function and only then to decide how to measure these categories would indeed follow the accepted principles how to define rheumatological Core Sets.26 ICF Core Sets could therefore complement the current rheumatological Core Sets when defining functioning.

CONCLUSION In conclusion, the ICF is an exciting landmark for the assessment of the impact of musculoskeletal conditions on the individual. The ICF is not only a comprehensive and adequate framework to assess the impact of health conditions on an individual level but also on a population level. The ICF framework and applications such as the ICF Core Sets for RA are likely to be used in clinical practice, outcomes and rehabilitation research, education, health statistics and regulation.

Practice points † make use of the ICF framework to review, identify and describe patients problems, e.g. in multidisciplinary care settings. Use condition-specific ICF Core Sets to check for problems typically encountered in patients with that condition † carefully select health status instruments when formally evaluating disease consequences and treatment effectiveness in clinical studies or quality management. When deciding on an instrument, look at the instruments and the items individually and do not only read the information regarding its metric properties † when using health status instruments in clinical studies you may still want to look at the instruments and not only scores. Looking at individual items may provide you with an understanding of patients’ problems and needs

Research agenda † currently we are faced with ‘competing’ instruments in many areas. The mapping of items to the ICF provides a unique opportunity to standardize items

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and instruments. A uniform language will also help to avoid redundancies and therefore inefficiency when administering several, partially overlapping, health status instruments † instruments used in the evaluation of drug and surgical treatments may not be ideal for the assessment of functioning and health and the evaluation of multidisciplinary care. ICF based approaches, which cover not only body functions and activities but participation, personal factors and contextual factors may be more appropriate in these settings † testing of the first version of the ICF Sets from the perspective of different professions and in different countries † testing of the ICF Sets in the view of patients and in different clinical settings

ACKNOWLEDGEMENTS The authors are thankful to the Editors of Osteoarthritis and Cartilage and the Editor of the Journal of Rehabilitation Medicine for granting permission to use extracts, tables and figures of previously published materials in this article.

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