Background/Purpose: Up to 30% of patients with psoriasis (Ps) may develop psoriatic arthritis (PsA); ranging from mild and non-destructive disease to severe and erosive arthritis.¹ Spondylitis prevalence in PsA is approximately 25-30%. PREPARE, an international, multicenter, non-interventional study assessed PsA prevalence in patients presenting to dermatologists with Ps (285/949 had PsA, 117/285 = newly diagnosed; the Toronto Psoriatic Arthritis Screen [ToPAS] and Psoriasis and Arthritis Screening Questionnaire [PASQi] detected probable PsA in 42.9% and 45.1% of patients).² Since no formal assessment of inflammatory back pain (IBP) formed part of the PREPARE study, the focus of these post-hoc analyses was to determine if positive IBP correlated with PsA diagnosis as a useful screening tool.

Methods: Our analyses included patients with Ps who received either the PASQi or ToPAS screening questionnaires during their dermatologist’s visit. Patients were subsequently evaluated by a rheumatologist to establish/exclude a clinical diagnosis of PsA. The prevalence of IBP was identified by the PASQi and ToPAS questionnaires: PASQi back pain was defined by patients who “ever had back troubles” with stiffness lasting >30 minutes and IBP total score>4; ToPAS had 1 question addressing back pain occurrence lasting >3 months that was not injury related (although this was not included in the scoring of ToPAS). Cochran–Mantel–Haenszel (CMH) tests were used to analyze differences in proportions of positive IBP between PsA vs non-PsA groups.  Kappa coefficients determined the agreement between PsA diagnosis and positive IBP.

Results: Of the patients, 85/341 (24.9%) had positive PASQi defined IBP while 146/337 (43.3%) had positive ToPAS defined IBP. Patients with PsA detected by a rheumatologist/PASQi/ToPAS/a combination had higher IBP prevalence than Ps patients with no indication of PsA (32.6%-55.2% vs 17.6%-38.9%; Table). Of the patients with detected PsA or IBP, there was a higher extent of activity impairment in patients with IBP than those without IBP (PsA: 22.4% vs 15.75%, P=0.003; PASQi: 19.1% vs 16.2% P=0.3651 and ToPAS 23.5% vs 13.4% P=0.0003). Work productivity impairment was significantly higher in patients with PsA vs non-PsA (16.5% vs 10.9%, P=0.012) and positive vs negative IBP as detected by the ToPAS screen (19.1% vs 9.3%, P=0.003). All κ coefficients were <0.2 indicating slight agreement between IBP and PsA as defined by PASQi, ToPAS or a rheumatologist (Table).

Conclusion: In this study, Ps patients with PsA had increased IBP incidence compared to those without PsA. Kappa coefficients indicate that IBP is not a good marker for PsA diagnosis in patients with Ps. However, the high incidence of IBP detected in Ps patients warrants further investigation.

1.  Haroon, M et al. Ann Rheum Dis. 2013; 72:736-40

2.  Mease, PJ et al. Presented at EADV 2012, Prague, Czech Republic