Background/Purpose: There are few data in Spain evaluating the prevalence of psoriasis in the general population, accordingly there are not data evaluating the prevalence of psoriatic arthritis in Spain. Objetives: to estimate the prevalence of psoriasis and PsA in the general population. To estimate the prevalence of PsA in patients with cutaneous psoriasis, referred from the primary care and the prevalence in of PsA in the general population.

Methods: All patients identified with a diagnose code of cutaneous psoriasis or PsA, from the database of a primary care centre (San José from La Coruña, northwest of Spain) were invited to participate in the study by a telephonic call. Patients were evaluated in the following way: personal and family history, criteria for inflammatory back pain (IBP), spinal and peripheral pain (VAS), peripheral joint count: tender and swollen (78/76), metrology (cervical rotation (CR), occiput to wall distance (OW), lateral lumbar flexion (LLF), modified Schober (mS)), MASES, SF12, DLQI, PASI, BSA, `peripheral and axial x-rays, ESR, CRP, anti CCP and HLA-B27. Case definition was made according to clinical judgement. A descriptive analysis of the variables was performed. Prevalence estimates were obtained, together with their 95% confidence intervals. Adjustment to the prevalence figures was made based on detected erroneous psoriasis coding.

Results:

From a referral population of 36610 persons, 458 patients were identified with a code diagnosis of psoriasis or PsA. From those,  21 had already a diagnosis of PsA, 161 agreed to participate, 126 came to the hospital. From those, 4 patients were excluded because they do not have a diagnosis of psoriasis, at the end 122 psoriatic patients without arthritis were evaluated.

From a total of 122 patients studied, 12 patients were judged to have a clinical diagnosis of PsA. This leads to an estimated prevalence of PsA in psoriatic patients of 9.8% (95% IC: 4.1%-15.5%). From these figures, the estimated prevalence of cutaneous psoriasis in the general population was 1,2% (95% CI=1,1%-1,3%), whereas the prevalence of PsA in the general population taken into account all cases was 0,17% (95% CI=0,13%-0,21%). The prevalence of undiagnosed cases was 0,06% (95% CI=0,03%-0,08%). The clinical features of the patients 12 patients diagnosed as PsA were as follows: nail involvement: 25%, dactylitis 8.3%. Nocturnal and overall spinal pain past week 3.25±3.57 and 4.17±3.35, peripheral VAS 6.33±3.31, TJC 4.50±9.04, SJC 0.00, mS 4.48±1.03, OW 0.00, LLF 14.92±4.42. CR <70º: 8.3%, enthesitis 41,7%, PASI 0,33±1,15, BSA <10%: 100%, DLQI 1.42±1.56 SF12 physical 43.09±11.39, SF12 mental 39.28±12.11, ESR≤20 70%, CRP <0.8 80%, anti-CCP ≤25 100%, Negative FR 91.7%. Negative HLA-B27 91.7%. Peripheral erosions 18.2%, sacroiliitis grade II unilateral or higher 45.5%

Conclusion: In this study, the estimated prevalence of cutaneous psoriasis in a northern general population of Spain was 1.2%. The estimate (clinically judged) prevalence of psoriatic arthritis in patients with psoriasis was 9.8%, and the estimate prevalence of psoriatic arthritis in the general population was 0,17%, of these 0,06% of the cases may be undiagnosed.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/prevalence-of-psoriasis-and-psoriatic-arthritis-in-a-northern-population-of-spain/