The specificity of ultrasonography (US) for enthesitis in psoriatic arthritis (PsA) is unclear. The objective was to analyze the specificity of US enthesitis in Mode B and using Power Doppler (PD), for the diagnosis of PsA through a systematic review with meta-analysis. Systematic review in PubMed 2010-June 2023, of studies of adult patients with confirmed PsA with or without a control group of non-PsA patients, reporting information on US enthesitis. Data were analyzed on (a) the prevalence of US enthesitis (presence of at least one enthesitis) in PsA patients and non-PsA patients, (b) specificity and sensitivity of US enthesitis and then specifically PD for PsA diagnosis and (c) most specific localizations of enthesitis in PsA patients. Pooled percentages and means were evaluated using univariate random-effects meta-analysis. In 76 articles, 5,927 patients with PsA were compared to 3,423 controls (59.0% of whom had psoriasis). The prevalence of US enthesitis was 73.7% [95% confidence interval, 56.6%-90.9%] in PsA patients versus 12.6% [2.6%-22.3%] in controls. The pooled specificity and sensitivity of Mode B US were 73.2% [59.3%-87.0%] and 62.1% [47.9%-76.4%]; and of PD, were 97.9% [96.5%-99.5%] and 14.7% [8.2%-21.2%] respectively. The site most frequently involved in PsA but not in controls was the Achilles tendon, in which erosions and PD activity were most discriminant. In this systematic review, US enthesitis was highly prevalent in PsA patients. Evidencing enthesitis by US was found to be reasonably specific and could contribute to the diagnosis of PsA; PD was highly specific, however was rarely present.
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