Subgroups of fibromyalgia patients using the 1990 American College of Rheumatology criteria and the modified 2010 preliminary diagnostic criteria: the al-Ándalus project.

Objectives: We aimed to investigate the symptom profiles in subsets of fibromyalgia patients according to the subgroups created from the satisfaction of the 1990 American College of Rheumatology (ACR) diagnostic criteria (1990c) and/or the modified 2010 ACR preliminary diagnostic criteria (m-2010c).
Methods: A total of 913 (84 men) participants took part in this cross-sectional study. Participants were grouped as follows: i) 285 who did not fulfil any ACR diagnostic criteria (non-fibromyalgia); ii) 73 who fulfilled the 1990c only; iii) 96 who fulfilled the m-2010c only; iv) 459 who fulfilled both ACR diagnostic criteria. Experimental and clinical pain, chronic pain self-efficacy, pain catastrophising, fibromyalgia severity, fatigue, health-related quality of life, depression, state anxiety and physical fitness were assessed by means of several questionnaires and tests.
Results: Overall, the differences were consistent across all study outcomes (all, overall p<0.001), showing that the subgroup fulfilling both diagnostic criteria had the worst profile of all the subgroups, whereas those fulfilling any diagnostic criteria (non-fibromyalgia participants) had the most favourable results. Furthermore, the subgroup fulfilling the m-2010c only had a worse profile than the subgroup fulfilling the 1990c only, and presented similar but slightly better results than those fulfilling both diagnostic criteria.
Conclusions: Our results reinforce the understanding of fibromyalgia as a heterogeneous condition. Subgrouping of fibromyalgia patients is highly recommendable, since these subgroups show diverse clinical pictures and therefore treatment options should be individually tailored to their specific profile. The combination of 1990c and the m-2010c is potentially useful to identify subgroups of fibromyalgia patients.