Most ICF categories of the current version of the Comprehensive ICF Core Set for CWP
could be confirmed from the patient perspective by FM patients. Fifty-four ICF categories out of 67 categories of the Comprehensive ICF Core Set for CWP
were reported by the patients. Forty-eight additional categories that are not covered in the Comprehensive ICF Core Set for CWP
were raised. The present study also confirmed relevant outcomes of treatment in CWP and FM from the patient perspective, such as pain, fatigue, sleep disorders, psychological distress, lack of muscle power, difficulties changing and maintaining a body position, and difficulties carrying out a daily routine [29
]. Pain proved to be the central topic reported by patients, with a total of 159 concepts linked to the ICF Core Set category sensation of pain
Apart from pain, the most outstanding theme reported by participants was the attitude of others regarding FM. The patients describe often feeling left alone with their illness, due to a lack of understanding and acceptance from others. Several patients reported feeling as if FM is not accepted as a legitimate illness by some doctors and healthcare professionals and is often trivialized by friends, relatives and colleagues, thus adding to the burden of pain and exhaustion. Fifty-five concepts concerning negative attitudes of others regarding the illness were linked to the corresponding ICF Core Set categories (e410, e420, e425, e430, e450, e455). Forty-six additional concepts were linked to the first-level ICF category attitudes
(e4). Several studies report similar findings such as patients' experiences of stigma [31
] and studies documenting controversy as to the existence, classification and acceptance of FM by healthcare professionals [35
Thirteen ICF categories in the Comprehensive ICF Core Set for CWP were not at all mentioned by the focus groups. Most of the ICF categories belonged to Body Functions and included global psychosocial functions (b122), psychomotor function (b147), content of thought (b1602), proprioceptive function (b260) and haematological system functions (b430). Some categories were not confirmed but were linked to similar categories; for example, 18 concepts were linked to the category carrying out daily routine (d230) instead of undertaking multiple tasks (d220), and nine concepts were linked to intimate relationships (d770) instead of sexual functions (b640). Sometimes the participants made more specific statements that were linked to similar ICF categories; for example, although the ICF Core Set category societal attitudes (e460) was not linked, several statements were linked to categories e410 through e455 specifying individual attitudes (for example, individual attitudes of friends, colleagues, people in positions of authority, health professionals).
Forty-eight additional second-level ICF categories that are not covered in the current version of the Comprehensive ICF Core Set for CWP
were raised. Most of the additional ICF categories belong to Body Functions
, followed by Activities and Participation
and Environmental Factors
. Some of these additional ICF categories need special discussion. Several concepts deal with difficulties in cognitive functioning. Thirty-two concepts were linked to the Body Functions
category memory functions
(b144). The patients reported problems with short-term and long-term memory such as absorbing, storing and recalling information. Learning and applying knowledge was also perceived as challenging for the participants. Difficulties acquiring skills, thinking, hearing, listening and reading were frequently reported by the focus group participants. Poor memory performance and problems in cognitive functioning in FM sufferers have been well documented and are in accordance with other studies [39
]. Sensations associated with hearing, such as tinnitus and dizziness, were also reported by the participants, as in other studies [43
The use of the hands and arms is a further topic not included in the Comprehensive ICF Core Set for CWP that FM sufferers experience as very burdening. The participants reported difficulties in grasping, picking up and manipulating objects with their hands and pulling, reaching and turning or twisting the arms, making everyday activities and tasks very difficult to fulfil. Twenty-seven and 15 concepts were linked to fine hand use (d440) and hand and arm use (d445), respectively.
An additional topic found among the participants but not included in the Comprehensive ICF Core Set for CWP
was functions of the digestive system. Such problems included difficulties with salivation, swallowing and digesting food. Urinal and intestinal irregularities were frequently reported and experienced as extremely hindering, affecting numerous activities and participation in sports and social engagements. Irritable bowel syndrome and urinary problems in FM sufferers are reported in other studies as well [45
]. Twenty-two concepts were linked to functions related to the digestive system (b510 to b535). Some participants mentioned feeling as if fingers, hands, feet or legs were swollen although swelling was not always visible. These concepts were labelled not definable
. Other topics concerned Environmental Factors
not covered in the ICF classification (labelled not covered
). Numerous patients mentioned the benefits of heat, such as using hot or warm water to sooth aching body parts. Several others recognized the importance of exercise in coping with pain and fatigue.
The characteristics of the sample in this study (gender, age, disease duration) are comparable with samples in other national [48
] and international studies [49
]. The validation of the ICF Core Set for rheumatoid arthritis from the patient perspective using the same approach as in the present study showed similar results. Seventy-one out of the 76 ICF categories in the ICF Core Set for Rheumatoid Arthritis were confirmed and an additional 57 categories not covered in the ICF Core Set for rheumatoid arthritis emerged [20
It is important to mention that several strategies were used to improve and verify the trustworthiness of the data analysis. Triangulationensured the comprehensiveness of data; we included data triangulation by using two data analysts (investigator triangulation: multiple coding) [50
]. Secondly, reflexivity was assured by conducting a research diary for the documentation of memos concerning the design, data collection and data analysis. Clear exposition was also used, establishing guidelines for conducting the focus groups (including open-ended questions), verbatim transcription, and linking rules [28
]. Finally, peer review
was included, as described earlier. The kappa coefficient of 0.76 (0.70 to 0.82) for the accuracy of the peer review is comparable with other studies reporting kappa statistics about the linking of categories [22
], and can be regarded as substantial agreement.
There are some limitations of the present study that need special mention. The sample consists primarily of German residents. To establish a cross-cultural perspective we suggest that our methods be used in similar studies in other countries. Second, FM is a subtype of CWP, and may not be representative of all CWP conditions. Other ICF categories may have emerged if focus groups had been conducted with other CWP illnesses such as chronic fatigue or Gulf War syndrome. The controversy concerning the existence, classification and acceptance of FM interferes with the patients' need to be recognized and taken seriously with their illness. This may exacerbate symptoms and add to the burden of pain and exhaustion. Third, the linking process was performed by two psychologists according to established linking rules [28
]. Whether other health professionals would have decided differently, however, remains unclear. Finally, we conducted six focus groups following the strategy of saturation during data analyses, with the criteria of two consecutive focus groups each revealing less than 5% additional ICF categories in relation to the number of ICF categories of the Comprehensive ICF Core Set for CWP
identified in the respective previous focus group. Participants in a seventh focus group might still report new themes and concepts not yet addressed.
Initiatives such as the OMERACT address the challenge of standardizing and improving the quality of outcomes research by finding a common terminology and a common model of functioning and disability. The OMERACT FM workshop agreed upon the most important key domains to measure in FM. Some of the key domains mentioned are pain, patient global sense of well-being, fatigue, multidimensional aspects of functioning, sleep, depression, and treatment side effects. These domains are included in the Comprehensive ICF Core Set for CWP, which can in turn be used as a basis for the further specification of OMERACT domains and the development of new instruments to assess functioning for research. A further key research objective of the OMERACT initiative will be to include the patient perspective on what represents a clinically meaningful change in a domain or the syndrome as a whole. The present study can help enhance the knowledge of FM by including the patient perspective. Further research in the context of the development and confirmation of ICF Core Sets, however, is needed.
The results of the present study are comparable with the results of the validation of ICF Core Sets for rheumatoid arthritis. In line with the validation study of ICF Core Sets for CWP, most of the ICF categories included in the ICF Core Set for rheumatoid arthritis were also confirmed [20
]. In addition, both studies identified numerous ICF categories from the patient perspective that were not included in the current versions of the ICF Core Set. All results of the validation studies of ICF Core Sets will be presented at an international World Health Organization conference and will be taken into account for the decision on the final versions of ICF Core Sets.