There is a push for rheumatologists to use standardized tools, such as the Disease Activity Score (DAS), to measure disease activity in rheumatoid arthritis (RA) and to guide therapy.[1] However, permanent joint damage or noninflammatory pain syndromes such as fibromyalgia may affect the ability of tools that rely on patient-reported measures to accurately assess the level of active inflammatory joint disease and the subsequent need for alterations in immunomodulatory therapy. For example, a patient may self-report severe widespread pain and therefore have perceived high RA activity; however, in reality the active inflammation may be minimal and the patient needs less, not more, immunomodulation. These authors addressed this issue by examining the clinical impact of fibromyalgic symptoms on measures of disease activity in RA.
In this British study, 2 RA cohorts (1 with 105 patients and 2 with 100 patients; all meeting American College of Rheumatology criteria for RA[2]) were evaluated in a cross-sectional manner for the following: fibromyalgia tender points; pain (per visual analog scale); 28-joint count for tenderness and swelling; and other information, including erythrocyte sedimentation rate (ESR) to calculate disease activity by the DAS28, the clinical disease activity index (CDAI),[3] and the Health Assessment Questionnaire (HAQ).[4] The authors found that 18 of 105 patients in the first RA cohort and 12 of 100 patients in the second cohort met criteria for fibromyalgia in addition to RA (fibromyalgia criteria: ≥ 11 soft-tissue tender points). They also found that the number of tender but not swollen joints was a fair predictor of a patient having ≥11 soft-tissue tender points: a tender joint minus swollen joint count of ≥ 7 was 83% sensitive and 80% specific for fibromyalgia (as defined by ≥ 11 soft-tissue tender points) in the first cohort and 72% sensitive and 98% specific in the second cohort. Seventy-nine percent of patients with RA and fibromyalgia had a DAS28 score of ≥ 5.1, indicating active RA, vs only 20% of patients without fibromyalgia. However, when only swollen joints and the ESR were used to assess disease activity, only 29% of fibromyalgic patients with RA had active RA compared with 19% of patients without fibromyalgia (difference not significant).
The authors concluded that fibromyalgic features may lead to overestimation of disease activity, and they suggest that in patients with fibromyalgic RA, using swollen joints and biomarkers of inflammation may lead to more accurate assessment of RA activity. They also suggest that in terms of treatment, patients with fibromyalgic RA may need greater emphasis on non-disease-modifying antirheumatic drug therapy.
Certainly rheumatologists do not wish to use potentially toxic immunomodulatory therapy to treat noninflammatory symptoms, and this fascinating study is a step toward understanding how standardized measures of disease activity can be tailored to accurately assess disease activity in patients with RA who also have a component of fibromyalgia. However, although not statistically significant, it is interesting that even when only swollen joints and ESR were used, there was a higher percentage of fibromyalgic patients with active RA (29% vs 19%). Because accurately assessing the presence of synovitis on physical examination of a joint can be difficult, I wonder whether joint tenderness without perceived swelling may actually represent subtle synovitis. As a take-home point, this study can give us some guidance on how to assess disease activity in patients with both RA and fibromyalgia, but we’ll need more studies with more participants, as well as studies with better measures of "true" disease activity for comparison (perhaps including synovial biopsy; high-quality imaging to detect synovitis; or long-term studies of erosions, disability, or mortality) before we can have a universal approach for the assessment of inflammatory disease activity in patients with RA and fibromyalgia.
http://www.medscape.com/viewarticle/723106Thank you for this. I am actually dealing with exactly this issue today. My RD is waiting for blood work and wants to differentiate between RA and a diffuse pain syndrome...trying to learn about the latter now