Axial involvement is critical in psoriatic arthritis

The presence of axial involvement in patients with psoriatic arthritis (PsA) is associated with significantly worse disease status [1]. In the current study, axial involvement was identified in more than half of patients [2]. These results, awarded the best clinical poster, demonstrated that diagnostics of axial involvement are critical in clinical practice.

Dr Elena Gubar (Nasonova Research Institute of Rheumatology, Russia) and colleagues analysed disease activity and characteristics of patients with PsA with and without radiographic sacroiliitis in clinical practice.

Patients with PsA (n=385; 213 women and 172 men) according to CASPAR criteria were included. Median age was 45 years; median disease duration was 3.4 years. Patients were divided based on the presence of radiographic sacroiliitis, defined as bilateral grade ≥2 or unilateral grade ≥3:

• with radiographic sacroiliitis: n=214 (55.6%), 108 women and 106 men; and
• without radiographic sacroiliitis: n=171 (44.4%), 105 women and 66 men.

Differences were observed between these 2 groups. HLA-B27 antigen status was positive in 62 patients with radiographic sacroiliitis, compared with 26 patients without radiographic sacroiliitis (OR 1.9). Median tender joint count (TJC) was 9 in patients with radiographic sacroiliitis versus 6 in patients without radiographic sacroiliitis (P=0.02).

Disease activity was measured by Disease Activity Index for Psoriatic Arthritis (DAPSA) and Bath Ankylosing Spondylitis Disease Activity Index (BASDAI). In patients with radiographic sacroiliitis, DAPSA was higher in patients with versus without radiographic sacroiliitis (28.4 vs 20.0; P<0.05). BASDAI was 1.6 in patients with radiographic sacroiliitis versus 0, respectively (P<0.05). Leeds Enthesitis Index (LEI) was 0 in both patient groups. Dactylitis was present in 71 patients (33.2%) with radiographic sacroiliitis compared with 32 patients (18.7%) without radiographic sacroiliitis (OR 2.2). Furthermore, erosive radiographic arthritis of the feet occurred more often in patients with than without radiographic sacroiliitis (27.1% vs 17.0%; OR 1.8). The affected skin lesion area, evaluated in terms of body surface area (BSA) ≥3% was present in 120 patients with radiographic sacroiliitis and in 141 patients without (OR 0.6). Finally, the median C-reactive protein level in patients with radiographic sacroiliitis was 0.9 mg/dL, whereas in patients without radiographic sacroiliitis it was 0.8 mg/dL (P=0.03).

These results show that many differences are present between patients with and without radiographic sacroiliitis and that patients with radiographic sacroiliitis have more severe disease. Therefore, proper diagnostics of axial involvement are crucial.

1. Mease PJ, et al. J Rheumatol. 2018;45:1389–96.
2. Gubar E. Association of axial involvement with more severe disease status in psoriatic arthritis patients. Poster P6, 6^th World Psoriasis & Psoriatic Arthritis Conference, 30 June–3 July 2021.

 

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Posted on 17 September 202120 September 2021