Background/Purpose: Reported prevalence estimates of psoriatic arthritis (PsA) vary considerably, with few nationwide figures. This study aimed to estimate the prevalence of PsA among adults (18-79 years (y)) in Sweden 2017, overall, stratified by sex/age/education, and with contemporary need of specialized care, respectively. In the latter group, the proportion treated with disease-modifying anti-rheumatic drugs (DMARDs) was also assessed.

Methods: All individuals, 18-79y, alive and residing in Sweden on December 31, 2017, who had been seen in specialized care for clinically diagnosed PsA 1964-2017 were identified from 2 separate, overlapping sources: 1) individuals with ≥1 registered ICD diagnosis of PsA from out-/inpatient visits in the Swedish National Patient Register (NPR); 2) individuals registered with PsA in the Swedish Rheumatology Quality Register (SRQ). Data on the total Swedish population 2017, demographics, education (for individuals ≥30y), and treatments were retrieved from other registers. The base case (BC) PsA definition for prevalence estimation was ≥1 main ICD diagnosis of PsA (ICD-8:696.00; ICD-9:696A; ICD-10:L40.5/M07.0-M07.3) from a department of rheumatology or internal medicine (IM) in NPR, or a PsA diagnosis in SRQ. Sensitivity analysis definitions were: A) Liberal: ≥1 main or secondary ICD diagnosis of PsA from any department in NPR, or a PsA diagnosis in SRQ; B) As BC, but reducing the number of cases in line with a prior validation of the BC definition in which 86% of 400 cases fulfilled PsA classification criteria; C) As BC, but excluding cases with ≥1 main ICD diagnosis of rheumatoid arthritis from rheumatology or IM in NPR; D) Strict: ≥2 ICD diagnoses of PsA in NPR, of which ≥1 as main diagnosis from rheumatology or IM. Furthermore, the prevalence of PsA with contemporary need of specialized care was estimated by restricting the BC definition to 2015-2017 (≥1 main ICD diagnosis of PsA from rheumatology or IM in NPR or ≥1 visit in SRQ 2015-2017), and the proportion of this population with DMARD therapy in 2017 was assessed.

Results: A total of 29 359 cases, 18-79y, alive and residing in Sweden on December 31, 2017, with clinically diagnosed PsA according to the BC definition were identified, resulting in a national, prevalence of PsA in the adult (18-79y) population of 0.39%. Corresponding sensitivity analysis estimates ranged from 0.32-0.50%, with a validation-adjusted BC prevalence of 0.34% (Figure 1). Irrespective of age group, the PsA prevalence was numerically higher among females (Figure 2). Higher education was associated with numerically lower PsA prevalence ( >12y education: 0.38%; 10-12y:0.58%; ≤9y:0.54%, in adults ≥30y; BC PsA definition). The prevalence of PsA seen in specialized care 2015-2017 was estimated at 0.24%. In this population, 32% received biologic or targeted synthetic DMARDs, and 41% conventional synthetic DMARDs only, during 2017 (Figure 3).

Conclusion: The national prevalence of clinically diagnosed PsA in the adult (18-79y) Swedish population in 2017 was estimated at around 0.35% (0.32-0.39% across most definitions). Among the 62% of these patients who were seen in specialized care for PsA during the last 3 years of our study period, almost 3/4 received DMARD therapy in 2017.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-national-prevalence-of-clinically-diagnosed-psoriatic-arthritis-in-sweden-2017/