FM is common in RA, AxSpA and PsA. Comorbid FM appears to amplify DAS and could therefore influence management of these rheumatic conditions. 

Fibromyalgia (FM) is a complex neurosensory disorder characterized by persistent musculoskeletal pain, with numerous discrete tender points elicited on clinical examination. Besides, patients may also be experienced symptoms such as fatigue, sleep disturbances and anxiety. Females are more prone to FM is with an estimated prevalence of around 1–5% in the general population.

It was suggested that patients with inflammatory arthropathies commonly meet the criteria for FM. The exact prevalence of this concomitant FM in inflammatory arthropathy is still unclear. It is also unclear whether FM awakes as a complication of the index condition or occurs independently in sensitive individuals. Regardless of the underlying etiology, the presence of concomitant FM and its impact on the underlying inflammatory condition may be necessary. Presently the number of target specific drugs are used to achieve optimum reduction in disease activity or disease remission. Estimating disease activity in chronic inflammatory arthritis relies, in part, on self-assessment by the patient. Consequently, FM, which causes patients to experience pain independent of the inflammatory processes, may lead to inflated disease activity measures and, therefore, to inappropriate escalation, or improper stopping, of treatment in the underlying index rheumatic condition.

Rationale behind research:

None of the previous studies estimated the prevalence of FM in patients with inflammatory arthropathy.

Therefore, the present study was conducted to evaluate the prevalence and DAS of FM patients with inflammatory arthropathy.

Objective:

• To report the prevalence of FM in adult patients with chronic inflammatory arthritis
• The secondary aim is to compare DAS between those with and without FM within these index conditions, and thereby assess the impact of co-morbid FM on disease activity assessment

Study outcomes:

• Classification systems used to diagnose the index condition
• Important characteristics of the study patients (gender, age and disease duration)
• The prevalence of co-morbid FM, or DAS for patients with and without co-morbid FM

Time period: NA

In RA the prevalence of FM in RA, axSpA and PsA ranged from 4.9 to 52.4% (21% pooled), 4.11–25.2% (13% pooled in AS only) and 9.6–27.2% (18% pooled) respectively. The presence of concomitant FM was associated with higher DAS in patients with RA and AS (DAS28 mean difference 1.24, 95% CI: 1.10, 1.37 in RA; BASDAI mean difference 2.22, 95% CI: 1.86, 2.58 in AS). Concomitant FM was also associated with higher DAS in existing PsA studies. Self-reported, rather than objective, components of DAS appear to be raised in the presence of FM.

The present systematic review determined that concomitant FM is common in chronic inflammatory arthritis. We found the overall prevalence of FM in RA, AS and PsA to be 21%, 13% and 18% respectively.  Differences between diseases likely reflect the differing proportions of gender found naturally for each condition. RA affects more women, PsA occurs in men and women almost equally and AS is found predominantly in men. FM is strongly associated with female gender and as such corresponds to the relative prevalence estimates found in these inflammatory disorders.

Heterogeneity was high in the meta-analysis of concomitant FM prevalence, which suggests pooled results should be interpreted with caution. The meta-analysis was scaled by developed/non-developed populations, study sample selection methods and study risk of bias, but none of these factors had a significant impact on the amount of unexplained variability. Therefore, the variability in estimates is likely accounted for by the fact that studies differed by sample size, age and gender mix, all factors which are known to affect the prevalence of FM. Regardless of this variability, almost all individual studies reported rates of FM that were significantly higher than the general population.

In conclusion, the current meta-analysis review 40 papers and found that comorbid FM is much more prevalent in patients with RA, AxSpA or PsA. FM was significantly correlated with higher DAS but not with higher swollen joint count or laboratory (ESR, CRP) markers of disease activity. These scores are interpreted in combination with knowledge of the presence of concomitant FM to ensure optimal management and appropriate drug treatment.