Background/Purpose: Enthesitis is considered a hallmark of psoriatic arthritis (PsA), however data on the frequency and consequences of enthesitis are conflicting.

To analyze clinical enthesitis in PsA including its prevalence, scores used and localization through a systematic literature review with meta-analysis.

Methods: Systematic review in PubMed from January 2010 to June 2023, of studies of adult patients with confirmed PsA, reporting information on enthesitis (frequency, characteristics and/or consequences). Studies could be trials or observational studies, published in English.

Data collected at baseline, included (a) the prevalence of clinical enthesitis (i.e., frequency of having at least one active enthesitis), (b) scores used to assess enthesitis, (c) number of entheses involved per patient with enthesitis, (d) localization of enthesitis, assessed as localizations cited as a top 3 localization, and (e) impact of enthesitis on patient-reported outcomes and use of analgesics.

Univariate random-effects meta-analysis was performed to calculate pooled percentages and means in the overall population, by score used, and study type.

Results: Overall, 84,262 PsA patients from 212 studies (48 randomized controlled trials (RCTs), 164 observational studies) were analyzed. The weighted mean age and disease duration were 50.2 (SD 3.1) years and 7.7 (8.4) years, respectively; 52.6 % were women.

The pooled prevalence of enthesitis was 48.1% [95% confidence interval, 43.1-53.1]; heterogeneity was high (I² 100%). The prevalence was higher in RCTs (pooled prevalence 70.1% [65.6-74.6]) than in observational studies (30.4% [25.5-35.3]) and appeared similar in recent studies (Figure). Enthesitis was assessed through the Leeds Enthesitis Index (LEI) in 63.7% studies, the MASES (33.1%) and/or the SPARCC (29.3%). In 16 studies comparing the scores, the prevalence and the pooled number of entheses involved per patient varied according to the score used, between 59.6% [43.4 – 75.8] and 1.61 [1.42-1.81] for the LEI, and 62.3% [48.2 – 76.3] and 5.67 [5.28-6.06] for the SPARCC respectively. Most common sites for enthesitis were the Achilles tendon (part of the top 3 localizations in 64.5% studies), lateral epicondyle of the elbow (41.9%) and plantar fascia (25.8%). In 14 studies, the impact of enthesitis was studied: patients with vs without enthesitis had higher pain, fatigue, and analgesic use.

Conclusion: Enthesitis is a frequent manifestation in PsA, with a pooled prevalence of 48.1%; enthesitis was more prevalent in trials than in observational studies, reflecting recruitment patterns. The clinical assessment of enthesitis remains challenging, with heterogeneity in the scores used influencing the results: the most used score was the LEI which also led to the lowest prevalence of enthesitis and lowest number of entheses involved. The Achilles tendon was confirmed as the most frequent localization of enthesitis. Links with patients’ quality of life should be further explored. 

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/clinical-enthesitis-concerns-half-the-patients-with-psoriatic-arthritis-is-more-frequent-in-trials-than-in-observational-studies-and-is-assessed-heterogeneously-a-systematic-review-with-meta-analysi/