Abstract
In psoriatic arthritis (PsA) patients with concomitant chronic widespread pain, the differential diagnosis with fibromyalgia syndrome (FMS) can be challenging. We evaluated whether ultrasound (US) examination of entheseal sites can distinguish pain from (PsA) enthesitis versus FMS. PsA and FMS patients underwent clinical evaluation and gray-scale (GS; B-mode) and power Doppler (PD) US examination of the entheses. At least one enthesis with GS- and PD-mode changes was found in 90% and 59.3% of PsA patients (n = 140) and 62.7% and 35.3% of FMS patients (n = 51), respectively. GS and PD identified changes in 49.5% and 19.2% of the 840 PsA entheses and 22.5% and 7.9% of the 306 FMS entheses, respectively. Receiver operating characteristic curve analysis showed an area under the curve of 0.77 and 0.66 for B- and PD-mode, respectively, 3.5 being the best cut-off GS-score to discriminate the two conditions. Multivariate regression showed that Achilles and proximal patellar tendon enthesitis (B-mode) were strongly associated with PsA (odds ratio, ~2). Principal component analysis (B-mode) confirmed that PsA patients have a higher number of involved entheses and patterns of entheseal involvement than FMS patients. US evaluation of the entheses may help differentiate chronic widespread pain from PsA versus FMS.
Highlights
The diagnosis of fibromyalgia syndrome (FMS) in the majority of patients is based on the presence of chronic widespread pain (CWP)
The numbers of patients with psoriatic arthritis (PsA) and those with FMS enrolled in the ULISSE study were 140 and 51, respectively
In the PsA group, 70 patients (50%) were females; in the FMS group, 47 (92.2%) were females (p < 0.0001)
Summary
The diagnosis of fibromyalgia syndrome (FMS) in the majority of patients is based on the presence of chronic widespread pain (CWP). The 2016 revision confirmed that both CWP and somatic symptoms were needed to diagnose FMS and that “a diagnosis of fibromyalgia is valid irrespective of other diagnosis” [2] These criteria do not include the tender point evaluation (a key feature of the 1990 ACR classification criteria) [3] that is still widely used in daily practice to diagnose this syndrome. A recent study showed that compared with psoriatic arthritis (PsA), FMS was significantly associated with a high number of tender points and of somatic symptoms [5] This finding may be helpful in daily practice, it is still very difficult to understand the precise role of FMS and polyenthesitis in the individual patient with PsA and CWP
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