Validation of the International Classification of Functioning, Disability and Health (ICF) Core Set for rheumatoid arthritis from the patient perspective using focus groups

ar1956 ARJ Research article Validation of the International Classification of Functioning, Disability and Health (ICF) Core Set for rheumatoid arthritis from the patient perspective using focus groups Coenen Michaela michaela.coenen@med.uni-muenchen.de Cieza Alarcos alarcos.cieza@med.uni-muenchen.de Stamm A Tanja tanja.stamm@meduniwien.ac.at Amann Edda edda.amann@med.uni-muenchen.de Kollerits Barbara barbara.kollerits@med.uni-muenchen.de Stucki Gerold gerold.stucki@med.uni-muenchen.de

ICF Research Branch of the WHO Collaborating Center for the Family of International Classifications at the German Institute of Medical Documentation and Information (DIMDI), IHRS, Marchioninistraße 17, 81377 Munich, Germany

Department of Physical Medicine and Rehabilitation, University Hospital Munich, Marchioninistraße 15, 81377 Munich, Germany

Vienna Medical University, Department of Internal Medicine III, Division of Rheumatology, Waehringer Guertel 18–20, 1090 Vienna, Austria

Swiss Paraplegic Research (SPF), Nottwil, Switzerland

Arthritis Research & Therapy 1478-6354 2006 8 4 R84 http://arthritis-research.com/content/8/4/R84 1668437110.1186/ar1956 3 2 2006 14 3 2006 11 4 2006 12 4 2006 9 5 2006 2006 Coenen et al.; licensee BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Functioning is recognized as an important study outcome in rheumatoid arthritis (RA). The Comprehensive ICF Core Set for RA is an application of the International Classification of Functioning, Disability and Health (ICF) of the World Health Organisation with the purpose of representing the typical spectrum of functioning of patients with RA. To strengthen the patient perspective, persons with RA were explicitly involved in the validation of the Comprehensive ICF Core Set for RA using qualitative methodology. The objective of the study was twofold: to come forward with a proposal for the most appropriate methodology to validate Comprehensive ICF Core Sets from the patient perspective; and to add evidence to the validation of the Comprehensive ICF Core Set for RA from the perspective of patients. The specific aims were to explore the aspects of functioning and health important to patients with RA using two different focus group approaches (open approach and ICF-based approach) and to examine to what extent these aspects are represented by the current version of the Comprehensive ICF Core Set for RA. The sampling of patients followed the maximum variation strategy. Sample size was determined by saturation. The focus groups were digitally recorded and transcribed verbatim. The meaning condensation procedure was used for the data analysis. After qualitative data analysis, the resulting concepts were linked to ICF categories according to established linking rules. Forty-nine patients participated in ten focus groups (five in each approach). Of the 76 ICF categories contained in the Comprehensive ICF Core Set for RA, 65 were reported by the patients based on the open approach and 71 based on the ICF-based approach. Sixty-six additional categories (open approach, 41; ICF-based approach, 57) that are not covered in the Comprehensive ICF Core Set for RA were raised. The existing version of the Comprehensive ICF Core Set for RA could be confirmed almost entirely by the two different focus group approaches applied. Focus groups are a highly useful qualitative method to validate the Comprehensive ICF Core Set for RA from the patient perspective. The ICF-based approach seems to be the most appropriate technique.

Introduction

Functioning is recognized as an important study outcome in rheumatoid arthritis (RA). The number of clinical studies addressing functioning as a study endpoint in patients with RA has steadily increased during the past decade 1. These investigations have predominantly been guided by the medical perspective, from which the measurement of functioning and health is required to evaluate the patient-relevant outcomes of an intervention and from which functioning and health are seen primarily as a consequence of the disease 2. Many of these investigations include patient-oriented instruments, for example, patient and proxy self-reports on health status, quality of life, and health preferences. In rheumatology, the Health Assessment Questionnaire Disability Index (HAQ 3) and the Arthritis Impact Measurement Scales (AIMS2 4), which can be considered a generic instrument specific for RA, are widely used.

These instruments have also been developed according to the medical perspective and in line with the current concept in outcomes and quality-of-life research of condition-specific measures 5, that is, they are based on the assumption that different conditions are associated with salient patient problems in functioning. The individual influence of the environment and personal factors is, however, rarely taken into account 67. In addition, widely used RA-specific health-status measures, like the Health Assessment Questionnaire Disability Index, mainly address activities far more than participation 8. However, patients' experiences of functioning are determined by their interaction with the environment and their own personal characteristics and not only by the health condition 9101112. RA is also very much associated with the inability to continue working, ultimately leading to the experience of restriction in participation 13141516. Thus, a very comprehensive approach is required when addressing RA.

The bio-psycho-social model of Functioning, Disability and Health of the World Health Organization (WHO) 17 establishes the basis for a more comprehensive description of the experience of patients suffering from determined disease. Based on this model, functioning, with its components 'Body Functions', 'Body Structures' and 'Activities and Participation', is seen in relation to the health condition under consideration, as well as 'Personal Factors' and 'Environmental Factors' (Figure 1) 17. Functioning denotes the positive aspects, and disability the negative aspects of the interaction between an individual with a health condition and the contextual factors (Environmental Factors and Personal Factors) of that individual.

Figure 1

The bio-psycho-social model of functioning, disability and health

The bio-psycho-social model of functioning, disability and health.

This bio-psycho-social view guided the development of the International Classification of Functioning, Disability and Health (ICF), which was approved by the World Health Assembly (WHA) in May 2001. As the ICF has been developed in a worldwide, comprehensive consensus process over the past few years and was endorsed by the WHA as a member of the WHO Family of International Classifications, it is likely to become the generally accepted framework to describe functioning and health. The ICF is intended for use in multiple sectors that, besides health, include education, insurance, labour, health and disability policy, statistics, and so on. In the clinical context, it is intended for use in needs assessment, matching interventions to specific health states, rehabilitation and outcome evaluation. With the ICF, not only an etiologically neutral framework, but a globally agreed-on language and a classification is available to describe functioning on both the individual and population levels and from both the patient perspective and that of the health professionals. The ICF contains more than 1,400 so-called ICF categories, each allotted to the named components in the bio-psycho-social model with the exception of the component Personal Factors, which has not yet been classified. Each ICF category is denoted by a code composed by a letter that refers to the components of the classification (b, Body Functions; s, Body Structures; d, Activities and Participation; e, Environmental Factors) and is followed by a numeric code starting with the chapter number (one digit), followed by the 2nd level (two digits) and the 3rd and 4th levels (one digit each) (Figure 1).

All member states of the WHO are now called upon to implement the ICF in multiple sectors that, besides health, include education, insurance, labour, health-and-disability policy, statistics, and so on. However, the ICF has to be tailored to suit these specific applications 18. In the clinical context, the main challenge is the length of the classification with its over 1,400 categories. Mainly to address the issue of feasibility regarding the number of categories, ICF Core Sets have been developed in a formal decision making and consensus-based process integrating evidence gathered from preliminary studies for a number of the most burdensome, chronic health conditions, including RA 19. The preliminary studies included a Delphi exercise 20, a systematic review 21 on outcomes used in randomized clinical trials, which represents the view of researchers performing studies, and an empirical data collection, using the ICF checklist 22. Based on these studies, relevant ICF categories were identified. The lists of these identified categories represent the starting point of the decision-making and consensus process that took place at the consensus conference. The ICF Core Sets for patients with a determined health condition represent a selection of ICF categories out of the whole classification that can serve as minimal standards for the reporting of functioning and health for clinical studies and clinical encounters (Brief ICF Core Set) or as standards for multiprofessional, comprehensive assessment (Comprehensive ICF Core Set) under consideration of influential Environmental Factors. Since the ICF Core Sets address aspects within all the components of the ICF (Body Functions, Body Structures, Activities and Participation, Environmental Factors) they present a broad, condition-specific perspective that may reflect the whole health experience of patients. The current version of the Comprehensive ICF Core Set for RA includes 76 categories at the 2nd, 8 categories at the 3rd, and 12 categories at the 4th level of the classification. Regarding the 2nd level of the classification, 15 categories pertain to the component Body Functions, 8 categories to the component Body Structures, 32 categories to the component Activities and Participation and 21 categories to the component Environmental Factors 23. The Comprehensive ICF Core Set for RA describes the typical spectrum of problems in functioning among patients with RA encountered in comprehensive assessments or in clinical studies. Additionally, it provides an ideal basis from which to define theoretically sound models of functioning and disability in patients with RA.

The Comprehensive ICF Core Set for RA is now undergoing worldwide testing and validation using a number of approaches, including an international multicenter validation study and validation from the perspective of health professionals. One key aspect is the validation from the patient perspective. While the patient perspective has been implicitly included in the development of ICF Core Sets 22, the patients now will be explicitly involved in the process of the development and validation of ICF Core Sets. As standards of functioning and health in research and clinical practice, the ICF Core Sets have to show that they address the perspective of those who experience the disease.

Qualitative methodology provides the possibility to explore the perspective of those who experience a health problem, that is, the so-called patient perspective 2425. Qualitative methods are now widely used and increasingly accepted in health research and health-related sciences 262728. One of the most broadly used techniques in qualitative research is the focus group methodology 293031. Focus groups are "carefully planned series of discussions designed to obtain perceptions on a defined area of interest in a permissive, non-threatening environment" 32. They are especially useful for studies that involve complex issues that entail many levels of feeling and experience 33. "The basic goal in conducting focus groups is to hear from the participants about the topics of interest to the researcher" 34. The idea behind this methodology is that group processes can help people to explore and clarify their views 35. The non-directive nature of focus groups affords participants an opportunity to comment, explain, disagree and share experiences and attitudes 36.

The objective of the present study was twofold: first, to come forward with a proposal for the most appropriate focus group approach to validate Comprehensive ICF Core Sets from the patient perspective; and second, to add evidence to the validation of the Comprehensive ICF Core Set for RA from the perspective of patients with RA based on a group of German patients. The specific aims were to explore the aspects of functioning and health important to patients with RA using two different focus group approaches and to examine to what extent these aspects are represented by the current version of the Comprehensive ICF Core Set for RA.

Materials and methods

Design

We conducted a qualitative study with patients with RA using the focus group methodology. Two different focus group approaches were used, an open approach and an ICF-based approach. In the open approach, open-ended questions asking the patients to name their problems in Body Functions, Body Structures, and Activities and Participation were used. The patients were additionally asked about Environmental Factors (barriers and facilitators) influencing their everyday life (Table 1). In the ICF-based approach, each of the titles of the ICF chapters from which categories are included in the Comprehensive ICF Core Set for RA were presented. For each of the presented chapters, open-ended questions on possible problems in each of the life areas that the ICF chapters represent were used (Table 1). Finally, the patients were asked whether they thought anything was missing in the Comprehensive ICF Core Set for RA.

Table 1

Open-ended questions of the focus groups

Open-ended questions

If you think about your body and mind, what does not work the way it is supposed to?

If you think about your body, in which parts are your problems?

If you think about your daily life, what are your problems?

If you think about your environment and your living conditions,:

what do you find helpful or supportive?

what barriers do you experience?

The study was approved by the Ethics Commission of the Ludwig-Maximilian University, Munich.

Participants

All patients with RA diagnosed according to the revised American College of Rheumatology Criteria 37 who had been treated in the day clinic of the Department of Physical Medicine and Rehabilitation of the Ludwig-Maximilian University in Munich at any time since 2001 were contacted by mail and asked whether they would like to participate in the study. Participants were then selected from the list of all willing patients by the maximum variation strategy 38 based on the criteria disease duration and age group. Further participants were recruited from the German self-help service ('Deutsche Rheuma-Liga e.V.'). The group size was set at a maximum of seven persons to represent different opinions and facilitate interactions. Patients who participated in the focus groups gave written informed consent according to the Declaration of Helsinki 1996.

Sample size

The sample size was determined by saturation 38. Saturation refers to the point at which an investigator has obtained sufficient information from the field 32 (see Data analysis: saturation of data).

Data collection

All groups were conducted in a non-directive manner by the same moderator (MC) and one group assistant (EA, 'open approach'; BK, 'ICF-based approach'). Moderator and group assistants were psychologists with expertise in the ICF and in conducting group processes.

The focus groups were conducted according to focus group guidelines, including open-ended questions and further instructions (for example, introduction, procedure of the session, technical aspects). At the beginning of each focus group, the procedure of the session was explained, and the concept of the ICF was presented in lay terms to all participants. Then one of the two different focus group approaches was performed (open approach or ICF-based approach). The open-ended questions or the titles of the chapters (ICF-based approach) were presented visually to the participants by a Microsoft PowerPoint presentation. At the end of each focus group, a summary of the main results was given back to the group to enable the participants to verify and amend emergent issues.

The focus groups were digitally recorded and transcribed verbatim with an Olympus DSS system. The assistants observed the process within the group. Additionally, they filled in field notes according to a standardized coding schema. Field notes refer descriptive observations of the group interaction and of the topics of discussion. After each focus group a debriefing with moderator and assistant took place to review the course of the focus group.

The two focus group approaches were conducted alternately.

Data analysis

Qualitative analysis

The meaning condensation procedure 39 was used for the qualitative analysis of data. In the first step, the transcripts of the focus groups were read through to get an overview over the collected data. In the second step, the data were divided into units of meaning, and the theme that dominated a meaning unit was determined. A meaning unit was defined as a specific unit of text either a few words or a few sentences with a common theme 40. Therefore, a meaning unit division did not follow linguistic grammatical rules. Rather, the text was divided where the researcher discerned a shift in meaning 39. In the third step, the concepts contained in the meaning units were identified. A meaning unit could contain more than one concept.

Linking to the ICF

According to the purpose of multiple coding, the identified concepts were linked to the categories of the ICF by two health professionals (open approach, MC and EA; ICF-based approach, MC and BK) based on established linking rules 67, which enable linking concepts to ICF categories in a systematic and standardized way (Table 2). According to these linking rules, health professionals trained in the ICF are advised to link each concept to the ICF category representing this concept most precisely. One concept could be linked to one or more ICF categories, depending on the number of themes contained in the concept. Consensus between the two health professionals was used to decide which ICF category should be linked to each identified concept. In case of a disagreement, a third person trained in the linking rules was consulted. In a discussion led by the third person, the two health professionals that linked the concepts stated their pros and cons for the linking of the concept under question to a specific ICF category. Based on these statements, the third person made an informed decision.

Table 2

Scheme of the qualitative data analysis

Transcription

Meaning unit

ICF category

Moderator:

If you think about your body, what functional problems do you have?

Patient A:

I used to go to sports very often. Now I can't anymore. I even had to quit swimming

Restriction of sports Quit swimming

d9201 sports d4554 swimming

Patient B:

Exactly! I also had to quit swimming.

Patient C:

I can no longer cycle. (...)

Quit cycling

d4750 driving human-powered transportation

Moderator:

If you think about your body, where are your biggest problems?

Patient C:

Toes, ankle joints, knee joints, fingers

Toes

Ankle joints

s7502 structure of ankle & foot

s75021 ankle joint & joints of foot and toes

Knee joints

s75011 knee joint

Fingers

s7302 structure of hand

Patient A:

What bothers me are my wrists. (...)

Wrists

s73021 joints of hand and fingers

The transcription undergoes qualitative analysis to derive a meaning unit that is then linked to an International Classification of Functioning, Disability and Health (ICF) category.

Saturation of data

In this study saturation was defined as the point during data collection and analysis when the linking of the concepts of two consecutive focus groups reveals no additional 2nd level categories of the Comprehensive ICF Core Set for RA with respect to previous focus groups. Saturation was checked separately for the two approaches.

Confirmation of the ICF categories contained in the Comprehensive ICF Core Set for RA

An ICF category of the Comprehensive ICF Core Set for RA was regarded as confirmed if the identical or a similar category emerged from the focus groups (for example, s299 eye, ear and related structures, unspecified confirmed by s230 structures around eye). Since the ICF categories are arranged in a hierarchical code system, the 2nd level categories of the Comprehensive ICF Core Set for RA were considered confirmed when the corresponding 3rd or 4th level category of which they were a member had been named by the patients.

Accuracy of the analysis

To audit the accuracy of the analysis, 15% of the transcribed text was randomly selected, analyzed according to the meaning condensation procedure, and linked to the ICF by two health professionals (MC and TS) as a peer review. This process was performed in addition to the process described in the section 'Linking to the ICF'. The degree of agreement between the two investigators regarding the identified and linked concepts in this random selected text was calculated by kappa statistic with 95%-bootstrapped confidence intervals 4142. The values of the kappa coefficient generally range from 0 to 1, where 1 indicates perfect agreement and 0 indicates no additional agreement beyond what is expected by chance alone. The data analysis was performed with SAS for windows V9.1 (SAS Institute Inc., Cary, NC, USA).

Results

Description of the focus groups

A total of 49 participants were included in the focus groups (open approach, n = 25; ICF-based approach, n = 24). Participants' characteristics are summarized in Table 3. Ten focus groups with five groups in each approach were conducted. The focus group sessions lasted from about fifty minutes to two hours, including a short break. Regarding the categories of the Comprehensive ICF Core Set for RA, saturation of data was reached in both approaches after conducting five focus groups (Figure 2).

Figure 2

Saturation of the qualitative data in the focus groups

Saturation of the qualitative data in the focus groups. ICF, International Classification of Functioning, Disability and Health.

Table 3

Characteristics of participants and focus groups

Focus groups

Total

Open approach

ICF-based approach

Number of participants (n)

Mean age, year (range)

59 (24–81)

54 (35–75)

57 (24–81)

Gender (% female)

Mean disease duration, year (range)

16 (4–38)

15 (3–56)

Number of focus groups (n)

Mean session duration, hours:minutes (range)

1:09 (0:52–1:15)

1:35 (1:17–2:06)

1:22 (0:52–2:06)

ICF, International Classification of Functioning, Disability and Health.

Qualitative analysis and linking

A total of 1,900 relevant concepts were identified in the two approaches (open approach, n = 897; ICF-based approach, n = 1,003). These concepts were linked to 342 different ICF categories. For 155 of the 342 categories at the 3rd and 4th level of the classification, the corresponding 2nd level categories were considered (n = 66). Thus, the concepts were linked to a total of 253 2nd level categories. Fifty-two concepts named by the participants were more specific than the corresponding most specific ICF category (for example, jaw joint, problems with climbing upstairs). Regarding the categories of the chapter 'sensory functions and pain' (b2), for example, the participants reported several issues according to the pain quality (pressure pain, rest pain, stabbing pain), which are not specifically covered by the existing ICF categories. Therefore, all these concepts referring to different qualities of pain were linked to the ICF category 'b280 sensation of pain'.

Thirty-two concepts could not be linked to ICF categories (for example, quality of life in general, aspects of coping, disease management, time-related aspects, and variability of functioning). Fifteen of them could be allotted to the component Personal Factors, which has not yet been classified.

Confirmation of the Comprehensive ICF Core Set for RA

In total, 74 out of the 76 2nd level categories included in the Comprehensive ICF Core Set for RA were confirmed by the two focus group approaches (open approach, n = 65; ICF-based approach, n = 71). All 2nd level categories of the components Body Functions (n = 15) and Body Structures (n = 8) that are included in the Comprehensive ICF Core Set for RA were reported by the patients in the ICF-based focus group approach (Tables 4 to 7; categories in bold typeface).

Table 4

Body Functions (b): patients' reporting of ICF categories (2^ndlevel)

ICF categories

Reported by patients

Code

Title

Open approach

ICF-based approach

b126

Temperament and personality functions

Yes

b130

Energy and drive functions

Yes

b134

Sleep functions

Yes

b140

Attention functions

Yes

b147

Psychomotor functions

Yes

b152

Emotional functions

Yes

b160

Thought functions

Yes

b180

Experience of self and time functions

Yes

b210

Seeing functions

Yes

b215

Functions of structures adjoining the eye

Yes

b220

Sensations associated with the eye and adjoining structures

Yes

b230

Hearing functions

Yes

b240

Sensations associated with hearing and vestibular function

Yes

b250

Taste function

Yes

b255

Smell function

Yes

b265

Touch function

Yes

b270

Sensory functions related to temperature and other stimuli

Yes

b280

Sensation of pain

Yes

b320

Articulation functions

Yes

b410

Heart functions

Yes

b430

Haematological system functions

Yes

b435

Immunological system functions

Yes

b455

Exercise tolerance functions

Yes

b460

Sensations associated with cardiovascular and respiratory functions

Yes

b510

Ingestion functions

Yes

b515

Digestive functions

Yes

b520

Assimilation functions

Yes

b525

Defecation functions

Yes

b530

Weight maintenance functions

Yes

b535

Sensations associated with the digestive system

Yes

b540

General metabolic functions

Yes

b545

Water, mineral and electrolyte balance functions

Yes

b610

Urinary excretory functions

Yes

b620

Urination functions

Yes

b640

Sexual functions

Yes

b710

Mobility of joint functions

Yes

b715

Stability of joint functions

Yes

b730

Muscle power functions

Yes

b740

Muscle endurance functions

Yes

b760

Control of voluntary movement functions

Yes

b770

Gait pattern functions

Yes

b780

Sensations related to muscles and movement functions

Yes

b810

Protective functions of the skin

Yes

b820

Repair functions of the skin

Yes

b840

Sensation related to the skin

Yes

b850

Functions of hair

Yes

b860

Functions of nails

Yes

International Classification of Functioning, Disability and Health (ICF) categories of the ICF Core Set for rheumatoid arthritis are shown in bold typeface.

Table 5

Body Structures (s): patients' reporting of ICF categories (2^ndlevel)

ICF categories

Reported by patients

Code

Title

Open approach

ICF-based approach

s299

Eye, ear and related structures, unspecified (s220)^a

Yes

s320

Structure of mouth

Yes

s410

Structure of cardiovascular system

Yes

s530

Structure of stomach

Yes

s540

Structure of intestine

Yes

s710

Structure of head and neck region

Yes

s720

Structure of shoulder region

Yes

s730

Structure of upper extremity

Yes

s750

Structure of lower extremity

Yes

s760

Structure of trunk

Yes

s770

Additional musculoskeletal structures related to movement

Yes

s810

Structure of areas of skin

Yes

s830

Structure of nails

Yes

International Classification of Functioning, Disability and Health (ICF) categories of the ICF Core Set for rheumatoid arthritis are shown in bold typeface.

Table 6

Activities and Participation (d): Patients' reporting of ICF categories (2nd level)

ICF categories

Reported by patients

Code

Title

Open approach

ICF-based approach

d163

Thinking

Yes

d166

Reading

Yes

d170

Writing

Yes

d210

Undertaking a single task

Yes

d230

Carrying out daily routine

Yes

d240

Handling stress and other psychological demands

Yes

d330

Speaking

Yes

d360

Using communication devices and techniques

Yes

d410

Changing basic body position

Yes

d415

Maintaining a body position

Yes

d430

Lifting and carrying objects

Yes

d435

Moving objects with lower extremities

Yes

d440

Fine hand use

Yes

d445

Hand and arm use

Yes

d449

Carrying, moving and handling objects, other specified and unspecified (d430/d445)^a

Yes

d450

Walking

Yes

d455

Moving around

Yes

d460

Moving around in different locations (d455)^a

Yes

d465

Moving around using equipment

Yes

d470

Using transportation

Yes

d475

Driving

Yes

d510

Washing oneself

Yes

d520

Caring for body parts

Yes

d530

Toileting

Yes

d540

Dressing

Yes

d550

Eating

Yes

d560

Drinking

Yes

d570

Looking after one's health

d610

Acquiring a place to live

Yes

d620

Acquisition of goods and services

Yes

d630

Preparing meals

Yes

d640

Doing housework

Yes

d650

Caring for household objects

Yes

d660

Assisting others

Yes

d720

Complex interpersonal interactions

Yes

d750

Informal social relationships

Yes

d760

Family relationships

Yes

d770

Intimate relationships

Yes

d850

Remunerative employment

Yes

d859

Work and employment, other specified and unspecified (d850)^a

Yes

d910

Community life

Yes

d920

Recreation and leisure

Yes

International Classification of Functioning, Disability and Health (ICF) categories of the ICF Core Set for rheumatoid arthritis are shown in bold typeface. ^aConfirmation according to similar categories

Table 7

Environmental Factors (e): patients' reporting of ICF categories (2nd level)

ICF categories

Reported by patients

Code

Title

Open approach

ICF-based approach

e110

Products or substances for personal consumption

Yes

e115

Products and technology for personal use in daily living

Yes

e120

Products and technology for personal indoor and outdoor mobility and transportation

Yes

e125

Products and technology for communication

Yes

e130

Products and technology for education

Yes

e135

Products and technology for employment

Yes

e150

Design, construction and building products and technology of buildings for public use

Yes

e155

Design, construction and building products and technology of buildings for private use

Yes

e160

Products and technology of land development

Yes

e165

Assets

Yes

e210

Physical geography

Yes

e225

Climate

Yes

e310

Immediate family

Yes

e315

Extended family

Yes

e320

Friends

Yes

e325

Acquaintances, peers, colleagues, neighbours and community members

Yes

e330

People in positions of authority

Yes

e340

Personal care providers and personal assistants

Yes

e345

Strangers

Yes

e350

Domesticated animals

Yes

e355

Health professionals

Yes

e360

Other professionals

e410

Individual attitudes of immediate family members

Yes

e420

Individual attitudes of friends

Yes

e425

Individual attitudes of acquaintances, peers, colleagues, neighbors and community members

Yes

e430

Individual attitudes of people in positions of authority

Yes

e445

Individual attitudes of strangers

Yes

e450

Individual attitudes of health professionals

Yes

e460

Societal attitudes

Yes

e465

Social norms, practices and ideologies

Yes

e510

Services, systems and policies for the production of consumer goods

Yes

e515

Architecture and construction services, systems and policies

Yes

e540

Transportation services, systems and policies

Yes

e555

Associations and organizational services, systems and policies

Yes

e560

Media services, systems and policies

Yes

e565

Economic services, systems and policies

Yes

e570

Social security services, systems and policies

Yes

e575

General social support services, systems and policies

Yes

e580

Health services, systems and policies

Yes

e590

Labor and employment services, systems and policies

Yes

International Classification of Functioning, Disability and Health (ICF) categories of the ICF Core Set for rheumatoid arthritis are shown in bold typeface.

Additional categories

Sixty-six 2nd level additional categories (open approach, n = 41; ICF-based approach, n = 57) that are not included in the current version of the Comprehensive ICF Core Set for RA were identified in the focus groups (Tables 4 to 7). Most of the additional categories derive from the component Body Functions (open approach, n = 19; ICF-based approach, n = 29) followed by Environmental Factors (open approach, n = 15; ICF-based approach, n = 16). Five additional categories in the open approach and eight additional categories in the ICF-based approach were reported by the participants as related to the component Activities and Participation. Two and four additional categories from the component Body Structures were reported in the open and the ICF-based approach, respectively.

Accuracy of the analysis

The kappa coefficient for the agreement between the two investigators (peer review) was 0.66. The 95%-bootstrapped confidence interval, which indicates the precision of the estimated kappa coefficient, was 0.61 to 0.73.

Discussion

The current version of the Comprehensive ICF Core Set for RA could be confirmed almost entirely from the patient perspective by the two different focus group approaches applied (open approach and ICF-based approach). This study also confirmed relevant outcomes of treatment in RA from the patient perspective (for example, pain, stiffness, fatigue, mobility, muscle strength, getting social support) 244344. However, some issues emerged from the patient perspective that have not yet been covered by the Comprehensive ICF Core Set for RA or even by the ICF classification. ICF categories of the Comprehensive ICF Core Set for RA not reported by the patients were 'd570 looking after one's health' and 'e360 other professionals (support and relationship)'.

Sixty-six additional 2nd level categories that are not covered in the current version of the Comprehensive ICF Core Set for RA were raised. Most of the additional categories belong to the component Body Functions followed by the component Environmental Factors. Some of these additional ICF categories need special discussion.

It is important to emphasize that several categories were named by the patients at a higher level of specification than the 2nd level of the ICF. Some of these more specific categories are included in the Comprehensive ICF Core Set for RA, and some are not 23. One of these very specific categories not included in the Comprehensive ICF Core Set for RA at higher levels of specification are 'fatigue' and 'fatiguability'. 'Fatigue' and 'fatiguability' were linked to the 3rd level category 'b1300 energy level' and 'b4552 fatiguability', which belong to the 2nd level categories 'b130 energy and drive functions' and 'b455 exercise tolerance functions', respectively. Fatigue was also identified as an area of particular importance to patients with RA at OMERACT (Outcome Measures in Rheumatoid Arthritis Clinical Trials) VI 2545, as patient-relevant outcome in RA 4446 and as an adverse effects of medication 4748. Our study might thus suggest that the categories 'b1300 energy level' and 'b4552 fatiguability' should be specifically and explicitly included in the Comprehensive ICF Core Set for RA. This suggestion is strengthened by the findings of an ICF Core Set validation study deriving individual interviews 49 and validation studies from the health-professionals perspective.

Numerous additional categories were related to side effects of medication, which are an important issue for satisfaction with treatment from the patient perspective 244350. The participants of the study explicitly attributed some categories from the components Body Functions and Body Structures to side effects. Some of these causal relationships can also be found in the literature as complications due to medication 515253545556575859 or as relevant problems from the patient perspective 6061. The question whether ICF categories concerning side effects of medication should be included in the Comprehensive ICF Core Set for RA has to be considered carefully. With the advent of new medications, new side effects may appear. On one hand, one has to keep in mind that the ICF Core Sets establish the standards of 'what to measure' in patients with RA independent of the treatment (one could even say independent of 'fashionable treatment'). On the other hand, the intake of medication and the suffering of side effects belong to the reality of patients with RA. Perhaps one solution to this dilemma could be the development of treatment-specific ICF Core Sets.

Within the component Environmental Factors numerous categories not included in the current version of the Comprehensive ICF Core Set for RA were reported by the patients. There is no doubt that social support is an important Environmental Factor for patients with RA 62. Several studies pointed out the relationship and interaction between social support and disease activity, pain or disability 636465.

The category 'e165 (financial) assets', which is not included in the current version of the Comprehensive ICF Core Set for RA, was reported by the participants in the focus groups and in the ICF Core Set validation study using individual interviews 49 as a relevant Environmental Factor. Economic consequences in relation to income reduction or to loss of paid work due to physical disability were also found to be an important issue to patients with RA in the literature 63666768. Within this context, it has to be taken into account that patients with RA in most countries also have substantial RA-related out-of-pocket medical expenditures for co-payments for prescribed drugs, over-the-counter drugs and costs to complementary and alternative medicine 6970.

With both approaches used in this study, we found a broad range of themes that could be linked to the corresponding categories. Both approaches performed satisfactory results; however, it is important to mention that some patient-sensitive issues were only reported in the ICF-based approach, for example, 'b535 sensations associated with the digestive system', 'b610 urinary excretory functions', 'b620 urination functions', 'b640 sexual functions', and 'd530 toileting'. Issues concerning mood, disease management and coping were reported in detail in the open approach. Comparing the two approaches, the ICF-based approach seems to be the appropriate technique to confirm the Comprehensive ICF Core Set for RA, particularly with regard to the coverage of the components Body Structures and Body Functions.

In qualitative research and studies with focus group methodology, sample sizes typically remain small because intensive data analysis is required 3032. A small sample size with a diverse range of participants (n = 49) was used to obtain the required level of rich and meaningful data. According to Curtis and colleagues 71, the small samples in qualitative research are studied intensively and typically generate a large amount of information. By keeping the questions open-ended, the moderator can stimulate useful trains of thought in the participants that were not anticipated 72. The focus groups in our study were composed of four to seven participants. We decided to include groups with few participants because of the complexity of the topic and the expertise of the participants according to the literature 73. With a small group size, each participant has a greater opportunity to talk, which is reported as an important aspect for the group dynamics in groups with elderly and ill participants 3074.

The characteristics of the sample in this study (gender, age, disease duration) are comparable to samples in other national 6275 and international studies 4363. It is important to mention that several strategies were used to improve and verify the trustworthiness of the qualitative data. Triangulation was used to ensure the comprehensiveness of data. We included different aspects of triangulation by using two approaches to focus groups (methodological triangulation) and two data analysts (investigator triangulation: multiple coding) 7677. Continuous data analysis was used according to Pope and colleagues 78. Reflexivity was assured by conducting a research diary for the documentation of memos concerning the design, data collection and analysis of the study. Clear exposition was used to establish guidelines for conducting the focus groups (including open-ended questions), verbatim transcription, and linking rules 67. Thus, a clear account of methods of data collection and analysis was assured. Finally, peer review was used. The kappa coefficient of 0.66 (0.61 to 0.73) for the accuracy of the peer review is comparable to other studies reporting kappa statistics about the linking of categories 49 and can be regarded as 'substantial agreement' 79.

There are also some limitations of this study that need special mention. The sample consists only of German participants. We conducted this study as a pilot study to develop an appropriate method to validate ICF Core Sets from the patient perspective. Our suggestion is that our methods could be used in similar studies in other countries to establish a cross-cultural perspective. Secondly, the linking process was performed by two health professionals according to established linking rules 67. However, it remains unclear whether other health professionals would have decided differently. Finally, we followed the strategy of saturation during data analyses with the criteria of two consecutive focus groups revealing no additional 2nd level categories in the Comprehensive ICF Core Set for RA with respect to previous focus groups. Participants in a sixth focus group still might report new themes and concepts not yet reported.

Further research in the context of the development and confirmation of ICF Core Sets is needed. The results of this study will be presented at an international WHO conference and will be taken into account for the decision on the final version of the Comprehensive ICF Core Set for RA. In addition, using this study as a starting point, we are currently conducting further focus group studies with RA patients in other countries to implement the international perspective of the ICF Core Sets. Finally, the results of this study have also influenced the protocol that establishes the methods to developing ICF Core Sets. From now on the collection of data from the patient perspective will be implemented in the preliminary phase of the development of ICF Core Sets 19.

Conclusion

It is extremely important to consider the patient perspective for the validation of the Comprehensive ICF Core Set for RA. The existing version of the Comprehensive ICF Core Set for RA with its selected categories could be confirmed almost entirely by the two different focus group approaches applied. Focus groups are a highly useful qualitative method to validate the Comprehensive ICF Core Set for RA from the patient perspective. The ICF-based approach, which uses the contents of the ICF Core Sets to structure the focus groups seems to be the most appropriate technique. Additional categories not represented in the Comprehensive ICF Core Set for RA emerged from the focus groups.

Abbreviations

ICF = International Classification of Functioning, Disability and Health; RA = rheumatoid arthritis; WHA = World Health Assembly; WHO = World Health Organization.

Competing interests

The authors declare that they have no competing interests.

Authors' contributions

MC conceived and organized the study and drafted the manuscript. TS participated in the development of the focus group guidelines, the drafting of the manuscript and was involved in the peer review. AC participated in the development of the study design and accompanied the study implementation. EA and BK shared the focus groups as assistants and undertook the task of linking the qualitative data to the ICF. GS was responsible for the overall design of the development and the validation of ICF Core Sets.

Acknowledgements

MC was supported by a grant of the German self-help organization 'Deutsche Rheuma-Liga e.V.' We would like to thank Mrs. Elke Ruschek for her excellent transcription of the recordings of the focus groups.

Understanding functioning, disability, and health in rheumatoid arthritis: the basis for rehabilitation care Cieza A Stucki G Curr Opin Rheumatol 2005 17 183 189 10.1097/01.bor.0000151405.56769.e4 15711233 Value and application of the ICF in rehabilitation medicine Stucki G Ewert T Cieza A Disabil Rehabil 2002 24 932 938 10.1080/09638280210148594 12523361 Measurement of patient outcome in arthritis Fries JF Spitz P Kraines RG Holman HR Arthritis Rheum 1980 23 137 145 7362664 AIMS 2 Meenan RF Mason JH Anderson JJ Guccione AA Kazis LE Arthritis Rheum 1992 35 1 10 1731806 Measuring health-related quality of life Guyatt GH Feeny DH Patrick DL Ann Intern Med 1993 118 622 629 8452328 Linking health-status measurements to the International Classification of Functioning, Disability and Health Cieza A Brockow T Ewert T Amman E Kollerits B Chatterji S Üstün TB Stucki G J Rehabil Med 2002 34 205 210 10.1080/165019702760279189 12392234 ICF linking rules: an update based on lessons learned Cieza A Geyh S Chatterji S Kostanjsek N Üstün B Stucki G J Rehabil Med 2005 37 212 218 16024476 10.1080/16501970510040263 The International Classification of Functioning, Disability and Health (ICF) Core Sets for rheumatoid arthritis: a way to specify functioning Stucki G Cieza A Ann Rheum Dis 2004 63 Suppl 2 ii40 ii45 10.1136/ard.2004.028233 15479870 Beyond disability: measuring the social and personal consequences of osteoarthritis Carr A Osteoarthritis Cartilage 1999 7 230 238 10.1053/joca.1998.0154 10222222 The role of environment in the International Classification of Functioning, Disability and Health (ICF) Schneidert M Hurst R Miller J Üstün B Disabil Rehabil 2003 25 588 595 10.1080/0963828031000137090 12959332 The subjective dimension of functioning and disability: what is it and what is it for? Ueda S Okawa Y Disabil Rehabil 2003 25 596 601 10.1080/0963828031000137108 12959333 The International Classification of Functioning, Disability and Health: a new tool for understanding disability and health Üstün TB Chatterji S Bickenbach J Kostanjsek N Schneider M Disabil Rehabil 2003 25 565 571 10.1080/0963828031000137063 12959329 Socio-economic consequences of rheumatoid arthritis in the first years of the disease Albers JM Kuper HH van Riel PL Prevoo ML van't Hof MA van Gestel AM Severens JL Rheumatology (Oxford) 1999 38 423 430 10.1093/rheumatology/38.5.423 10371280 Work disability in rheumatoid arthritis 10 years after the diagnosis Sokka T Kautiainen H Mottonen T Hannonen P J Rheumatol 1999 26 1681 1685 10451062 How does functional disability in early rheumatoid arthritis (RA) affect patients and their lives? Results of 5 years of follow-up in 732 patients from the Early RA Study (ERAS) Young A Dixey J Cox N Davies P Devlin J Emery P Gallivan S Gough A James D Prouse P Rheumatology (Oxford) 2000 39 603 611 10.1093/rheumatology/39.6.603 10888704 The impact of rheumatoid arthritis on life activities Katz PP Arthritis Care Res 1995 8 272 278 8605266 World Health Organization International Classification of Functioning, Disability and Health: ICF Geneva: WHO 2001 Application of the International Classification of Functioning, Disability and Health (ICF) in clinical practice Stucki G Cieza A Ewert T Kostanjsek N Chatterji S Üstün TB Disabil Rehabil 2002 24 281 282 10.1080/09638280110105222 12004974 ICF Core Sets development for patients with chronic conditions Cieza A Ewert T Üstün TB Chatterji S Kostansjek N Stucki G J Rehabil Med 2004 44 Suppl 9 11 15370742 Identification of relevant ICF categories in patients with chronic health conditions: A Delphi exercise Weigl M Cieza A Andersen C Kollerits B Amann E Stucki G J Rehabil Med 2004 44 Suppl 12 21 15370743 10.1080/16501960410015443 Identifying the concepts contained in outcome measures of clinical trials on musculoskeletal disorders and chronic wide spread pain using the International Classification of Functioning, Disability and Health as a reference Brockow T Cieza A Kuhlow H Sigl T Franke T Harder M Stucki G J Rehabil Med 2004 44 Suppl 30 36 15370745 10.1080/16501960410015371 Identification of the most common patient problems in patients with chronic conditions using the ICF checklist Ewert T Fuessl M Cieza A Andersen C Chatterji S Kostanjsek N Stucki G J Rehabil Med 2004 44 Suppl 22 29 15370744 10.1080/16501960410015362 ICF Core Sets for rheumatoid arthritis Stucki G Cieza A Geyh S Battistella L Lloyd J Symmons D Kostanjsek N Schouten J J Rehabil Med 2004 44 Suppl 87 93 10.1080/16501960410015470 15370754 Rheumatology outcomes: the patient's perspective Carr AJ Hewlett S Hughes R Mitchell H Ryan S Carr M Kirwan J J Rheumatol 2003 30 880 883 12672221 Outcomes from the Patient Perspective Workshop at OMERACT 6 Kirwan J Heiberg T Hewlett S Hughes R Kvien T Ahlmen M Boers M Minnock P Saag K Shea B J Rheumatol 2003 30 868 872 12672218 Qualitative research in health care: Assessing quality in qualitative research Mays N Pope C BMJ 2000 320 50 52 1117321 10617534 10.1136/bmj.320.7226.50 Users' guides to the medical literature: XXIII. Qualitative research in health care, A. Are the results of the study valid Giacomini MK Cook DJ JAMA 2000 284 357 362 10891968 10.1001/jama.284.3.357 Murphy E Dingwall R Greatbatch D Parker S Watson P Qualitative Research Methods in Health Technology Assessment: a Review of the Literature Southampton: Health Technology Assessment 1998 2 16 Collecting and analysing qualitative data: issues raised by the focus group Sim J J Adv Nurs 1998 28 345 352 10.1046/j.1365-2648.1998.00692.x 9725732 Morgan DL Focus Groups as Qualitative Research Thousand Oaks: Sage; Qualitative Research Methods 2 1997 Vaughn S Schumm JS Sinagub J Focus Group Interviews in Education and Psychology Thousand Oaks: Sage 1996 12294359 Krueger RA Casey MA Focus Groups: a Practical Guide for Applied Research Thousand Oaks: Sage 2000 Morse JM Critical Issues in Qualitative Research Methods Thousand Oaks: Sage 1994 When to use focus groups and why Morgan DL Krueger RA Successful Focus Groups: Advancing the State of the Art Newbury Park: Sage Morgan DL 1993 3 19 Qualitative research: Introducing focus groups Kitzinger J BMJ 1995 311 299 302 7633241 Focus groups in mental health research: enhancing the validity of user and provider questionnaires Powell RA Single HM Lloyd KR Int J Soc Psychiatry 1996 42 193 206 8889643 The American Rheumatism Association 1987 revised criteria for the classification of rheumatoid arthritis Arnett FC Edworthy SM Bloch DA McShane DJ Fries JF Cooper NS Healey LA Kaplan SR Liang MH Luthra HS Arthritis Rheum 1988 31 315 324 3358796 Patton MQ Qualitative Evaluation and Research Methods Newbury Park: Sage 1990 Kvale S Interviews - An Introduction to Qualitative Research Interviewing California: Sage 1996 Karlsson G Psychological Qualitative Research from a Phenomenological Perspective Stockholm: Almquist & Wiskell International 1995 A coefficient of agreement for nominal scales Cohen J Educ Psychol Meas 1960 20 37 46 A SAS Macro for Calculating Bootstrapped Confidence Intervals About a kappa Coefficient http://www2.sas.com/proceedings/sugi22/STATS/PAPER295.PDF Rheumatology outcomes: the patient's perspective. A multicentre focus group interview study of Swedish rheumatoid arthritis patients Ahlmén M Nordenskiöld U Archenholtz B Thyberg I Rönnqvist T Lindén L Andersson A-K Mannerkorpi K Rheumatology 2005 44 105 110 10.1093/rheumatology/keh412 15381792 Arthritis care: Comparison of physicians' and patients' views Lambert BL Butin DN Moran D Zhao SZ Carr BC Chen C Kizis FJ Semin Arthritis Rheum 2000 30 100 110 10.1053/sarh.2000.9203 11071581 Patients' perspective Quest E Aanerud GJ Kaarud S Collins S Leong A Smedeby B Denny-Waters A Mellors R Taylor D de Witt M (Patient Perspective Group) J Rheumatol 2003 30 884 885 12672222 Impairment of quality of life: rheumatoid arthritis versus sarcoidosis Wirnsberger RM De Vries J Jansen TLThA Van Heck GL Wouters EFM Drent M Neth J Med 1999 54 86 95 10.1016/S0300-2977(98)00148-X 10189781 The use of methotrexate in rheumatoid arthritis Borchers AT Keen CL Cheema GS Gershwin ME Semin Arthritis Rheum 2004 34 465 483 10.1016/j.semarthrit.2003.12.003 15305245 Rheumatoid arthritis, new standards of care: nursing implications of infliximab Risley S Thomas MA Bray V J Orthop Res 2004 8 41 49 Validating the International Classification of Functioning, Disability and Health Comprehensive Core Set for rheumatoid arthritis from the patient perspective: a qualitative study Stamm TA Cieza A Coenen M Machold KP Nell VPK Smolen JS Stucki G Arthritis Rheum 2005 53 431 439 15934102 10.1002/art.21159 Factors influencing the beliefs of patients with rheumatoid arthritis regarding disease-modifying medication Goodacre LJ Goodacre JA Rheumatology 2004 43 583 586 10.1093/rheumatology/keh116 14970399 Antirheumatic therapy Deman AM Brooks PM Oxford Textbook of Rheumatology Oxford: Oxford University Press Maddison PJ, Isenberg DA, Woo P, Glass DN 1993 329 349 The use of leflunomide in the treatment of rheumatoid arthritis: an experimental and clinical review Schattenkirchner M Immunopharmacology 2000 47 291 298 10878295 10.1016/S0162-3109(00)00194-6 Drug modification of inflammation - non-steroidal anti-inflammatory drugs Brooks PM Oxford Textbook of Rheumatology Oxford: Oxford University Press Maddison PJ, Isenberg DA, Woo P, Glass DN 1993 323 328 Time dependent risk of gastrointestinal complications induced by non-steroidal anti-inflammatory drug use: a consensus statement using a meta-analytic approach Richy F Bruyere O Ethgen O Rabenda V Bouvenot G Audran M Herrero-Beaumont G Moore A Eliakim R Haim M Reginster JY Ann Rheum Dis 2004 63 759 766 10.1136/ard.2003.015925 15194568 Glucocorticoids in the treatment of early and late RA Bijlsma JWJ Boers M Saag KG Furst DE Ann Rheum Dis 2003 62 1033 1037 10.1136/ard.62.11.1033 14583563 Ocular complications of topical, peri-ocular, and systemic corticosteroids Carnahan MC Goldstein DA Curr Opin Ophthalmol 2000 11 478 483 11141645 Low-dose corticosteroid therapy in rheumatoid arthritis: balancing the evidence Saag KG Am J Med 1997 103 31S 39S 10.1016/S0002-9343(97)90006-1 9455967 Low dose long-term corticosteroid therapy in rheumatoid arthritis: An analysis of serious adverse events Saag KG Koehnke R Caldwell JR Brasington R Burmeister LF Zimmerman B Kohler JA Furst DE Am J Med 1994 96 115 123 10.1016/0002-9343(94)90131-7 8109596 Glucocorticoids Axelrod L Textbook of Rheumatology Philadelphia: WB Saunders Kelly WN, Harris ED, Ruddy S, Sledge GB 1993 779 796 Perceptions of the risks and benefits of medicines in patients with rheumatoid arthritis and other painful musculoskeletal conditions Berry D Bradlow A Bersellini E Rheumatology 2004 43 901 905 10.1093/rheumatology/keh196 15113996 Patients' perceptions of treatment with anti-TNF therapy for rheumatoid arthritis: a qualitative study Marshall NJ Wilson G Lapworth K Kay LJ Rheumatology 2004 43 1034 1038 10.1093/rheumatology/keh237 15150436 Loss of physical independence in rheumatoid arthritis: Interview data from a representative sample of patients in rheumatologic care Westhoff G Listing J Zink A Arthritis Care Res 2000 13 11 22 10.1002/1529-0131(200002)13:1<11::AID-ART4>3.0.CO;2-5 11094922 Socio-economic consequences of rheumatoid arthritis in the first years of the disease Albers JM Kuper HH van Riel PL Prevoo ML 't Hof MA van Gestel AM Severens JL Rheumatology 1999 38 423 430 10.1093/rheumatology/38.5.423 10371280 Stress system response and rheumatoid arthritis: a multilevel approach Walker JG Littlejohn GO McMurray NE Cutolo M Rheumatology 1999 38 1050 1057 10.1093/rheumatology/38.11.1050 10556255 Pain coping and social support as predictors of long-term functional disability and pain in early rheumatoid arthritis Evers AWM Kraaimaat FW Geenen R Jacobs JWG Bijlsma JWJ Behav Res Ther 2003 41 1295 1310 10.1016/S0005-7967(03)00036-6 14527529 Work disability in rheumatoid arthritis 10 years after the diagnosis Sokka T Kautiainen H Mottonen T Hannonen P J Rheumatol 1999 26 1681 1685 10451062 How does functional disability in early rheumatoid arthritis (RA) affect patients and their lives? Results of 5 years of follow-up in 732 patients from the Early RA Study (ERAS) Young A Dixey J Cox N Davies P Devlin J Emery P Gallivan S Gough A James D Prouse P Rheumatology 2000 39 603 611 10.1093/rheumatology/39.6.603 10888704 Work disability in early rheumatoid arthritis Doeglas D Suurmeijer T Krol B Sanderman R van Leeuwen M van Rijswijk M Ann Rheum Dis 1995 54 455 460 7632086 Direct costs related to rheumatoid arthritis: The patient perspective Huelsemann JL Mittendorf T Merkesdal S Zeh S Handelmann S von der Schulenburg J-M Zeidler H Ruof J Ann Rheum Dis 2005 64 1456 1461 10.1136/ard.2004.031880 15800007 Arthritis Cost and Outcome Project Group. Living with rheumatoid arthritis: expenditures, health status, and social impact on patients Lapsley HM March LM Tribe KL Cross MJ Courtenay BG Brooks PM Ann Rheum Dis 2002 61 818 821 10.1136/ard.61.9.818 12176807 Approaches to sampling and case selection in qualitative research: examples in the geography of health Curtis S Gesler W Smith G Washburn S Soc Sci Med 2000 50 1001 1014 10.1016/S0277-9536(99)00350-0 10714922 The design and analysis of focus group studies Knodel J Successful Focus Groups: Advancing the State of the Art Morgan DL. Newbury Park: Sage 1993 35 50 The future of focus groups Krueger RA Qual Health Res 1995 5 524 530 The group effect in focus groups: planning, implementing, and interpreting focus group research Carey AM Critical Issues in Qualitative Research Methods Thousand Oaks: Sage Morse JM 1994 225 241 The national database of the German Collaborative Arthritis Centres: I. Structures, aims, and patients Zink A Listing J Klindworth C Zeidler H Ann Rheum Dis 2001 60 199 206 10.1136/ard.60.3.199 11171678 Denzin NK The Research Act: a Theoretical Introduction to Sociological Methods New York: McGraw-Hill 1978 Checklists for improving rigour in qualitative research: a case of the tail wagging the dog? Barbour R BMJ 2001 322 1115 1117 1120242 11337448 10.1136/bmj.322.7294.1115 Qualitative research in health care: Analysing qualitative data Pope C Ziebland S Mays N Br Med J 2000 320 114 116 The measurement of observer agreement for categorial data Landis JR Koch GG Biometrics 1977 33 159 174 843571