RESEARCH REPORT PLATFORM PRESENTATION

CLASSIFICATION OF PERSONS WITH FIBROMYALGIA: RELIABLE AND VALID SUBGROUPS BASED ON THE MULTIDIMENSIONAL PAIN INVENTORY (MPI-D). Verra M^1,2, Angst F², Brioschi R³, Lehmann S², Aeschlimann A^2,4; ¹Physiotherapy Department, RehaClinic, Zurzach, Switzerland. ²Research Department, RehaClinic, Zurzach, Switzerland. ³Clinical Psychology, RehaClinic, Zurzach, Switzerland. ⁴Rheumatology Department, RehaClinic, Zurzach, Switzerland

PURPOSE: The aims of this study were to investigate if it was possible to replicate and describe the three cluster solution and profiles found in other pain groups and describe cluster profiles based on self-reported Multidimensional Pain Inventory-scores for patients with fibromyalgia, describe characteristics of the cluster in relation to physical function, fear and depression, and coping at the same point in time and to validate the cluster solution by comparing clusters in physical function, fear and depression, and coping over time. RELEVANCE: Physical Therapists realise that the group of persons with fibromyalgia is extremely heterogeneous with regard to its etiology and responsiveness to interventions. The process of subclassification of fibromyalgia is a clinical reality but undertaken on a individual clinical level. Classification of persons with fibromyalgia into homogenous subgroups is an important objective in order to tailor interventions and to control for subgroup differences when evaluating treatment outcome. PARTICIPANTS: Eighty-five persons with fibromyalgia took part in the study. All persons were participants in the in-house Zurzach pain management programmes with a cognitive-behavioural approach, including physical exercise, and had no other diagnosis which could interfere with these rehabilitation activities. METHODS: The measures used were the Multidimensional Pain Inventory-German version (MPI-D), the Medical Outcomes Study Short Form 36-German version (SF-36), the Hospital Anxiety and Depression Scale-German version (HADS-D), and the Coping Strategies Questionnaire-German version (CSQ-D). ANALYSIS: Cluster analysis was conducted for the total sample MPI-D subscale scores. RESULTS: The adaptive copers cluster represented 23% of the sample, dysfunctional 47% of the sample, and interpersonally distressed 30% of the sample. The external validation of the cluster solution showed that there were several significant differences between clusters in physical function, fear and depression, and coping measures. There was also a significant interaction effect (cluster x time) in physical function (SF-36). Persons in the dysfunctional cluster reported decreased physical function over time. CONCLUSIONS: These results support the presence of different subgroups among persons with fibromyalgia. Future research will be needed to validate these outcomes on persons in different settings. IMPLICATIONS: This classification on psychosocial factors can be seen as a complement to a classification based on medical condition. We hypothesize, that subsequent randomized trials will demonstrate that effect sizes increase when classification and matching are taken into account. KEYWORDS: fibromyalgia, subgroups, MPI-D. FUNDING ACKNOWLEDGEMENTS: This work was funded by the SPA Rehabilitation Foundation. CONTACT: m.verra@rehaclinic.ch

ETHICS COMMITTEE: The study was approved by the local research ethics committee (Health Department in Aarau, Switzerland).