Fibromyalgia as a Modifying Factor of Clinical Course of Rheumatoid Arthritis

Introduction. Rheumatoid arthritis (RA) is one of the most common inflammatory joint disease, with a progressing severity and high disability. It is often combined with fibromyalgia (FM), which can modify its course. The prevalence of primary FM among adults is on average 2.0-3.0 %, with prevalence of females and peak age of 55-64 years. In recent years, the principles of diagnosis of FM have been revised, along with the traditional criteria ACR1990 the modified criteria mACR2010 were proposed, but there is practically no experience with their use in patients with RA. Aim. To find out the clinical features of patients with RA associated with FM, and the possible association of the course of the disease with FM markers according to the criteria ACR1990 and mACR2010. Materials and methods. 125 patients (100.0 % female) with RA were included in the study. In 46 of them RA was associated with FM. Mean age of the patients under investigation was 49.6 ± 12.8 years. The diagnosis RA was established by ACR/EULAR-2010 criteria, the diagnosis FM was established regarding ACR1990 and modified ACR2010 criteria. RA activity was evaluated by DAS28 and CDAI, functional status – by HAQ. The diagnosis of FM was given in the case of detecting at least 11 (out of 18) specific sensory points (CP ≥ 11) and 13 (from 31) on the scale of fibromyalgia (SF ≥ 13) in patients with RA. Specific CPs were determined by pressing with a finger at them with a force of 4 kg/cm2 (to the effect of whitening of the nail bed of the researcher) and were considered positive if the patient felt pain. Results and discussion. By the evaluation of clinical features of patients in which the rheumatoid arthritis (RA) was associated with fibromyalgia (FM) it was found that these patients had a higher disease activity by DAS28 and CDAI (OR = 13.3, 95% CI 4.41, 40.3). Significant violations of the physical function (HAQ>2) were found in 40.0 % of RA patients associated with FM, and in 19.0 % of patients with isolated RA. In the presence of FM in patients with RA the difference between the number of tender and swollen joints was 3.16 times higher and significantly correlated with the markers of the central sensitization (number of tender points fibromyalgianess scale). FM frequency was higher among the patients with seronegative RA (OR = 2.90, 95% CI 1.36, 6.21). Phenotypic features of patients with RA suggest the need for modification of diagnostic and therapeutic measures in patients with a fibromyalgic variant of the disease. Conclusions. FM is an independent factor that modifies the clinical course of the RA, causes an increased disease activity by DAS28 and CDAI, significantly impairs physical function for the RA patients.