Swollen joints better proxy for synovitis than tender joints in early PsA
medwireNews: Swollen joints are more likely to be associated with ultrasound (US)-confirmed synovitis than tender joints among DMARD-naïve individuals with early psoriatic arthritis (PsA), research suggests.
“Although early US imaging is an excellent confirmatory tool in the diagnosis and management of PsA, not all patients will undergo US in ‘real-world’ practice, due to several factors including lack of resources and time constraints,” explain the study authors.
Therefore, “clinicians frequently face challenging clinical decisions centred on disease activity status based on tender/swollen counts,” they add.
The study included 155 patients with early PsA (mean age 44 years, median symptom duration 1 year) who underwent clinical and US examination. Of the 5616 joints examined, 18.5% were tender, 9.8% were swollen, and 8.2% were both tender and swollen, while 20.4% had synovitis according to a gray scale (GS) grade of at least 2 on US, and 5.2% had synovitis according to a Power Doppler (PD) grade of 1 or higher. The majority of patients (98.1%) had GS-defined synovitis in at least one joint.
Helena Marzo-Ortega (University of Leeds, UK) and colleagues found that the prevalence of GS-defined synovitis was highest in joints that were both tender and swollen (44.4%), followed by those that were swollen without tenderness (36.4%) and those that were tender without swelling (25.7%), and was lowest in non-tender, non-swollen joints (subclinical synovitis; 16.9%).
When analyzed at the individual joint level, the degree of agreement between the presence of swelling and GS-defined synovitis was higher than that seen between tenderness and GS-defined synovitis, at 73.5–92.6% versus 51.0–87.4%, respectively.
Similarly, when the PD definition was used there was a higher level of agreement between swelling and synovitis (82.6–96.3%) than between tenderness and synovitis (72.9–91.1%). In general, the lowest level of agreement between clinical and US measures was seen in the feet.
Logistic regression analysis demonstrated that swelling was associated with a significantly higher likelihood of GS-defined synovitis (odds ratio [OR]=4.37 vs no swelling), whereas tenderness was not, irrespective of the presence of swelling. Both swelling (OR=8.78) and tenderness (OR=3.38) were independently associated with PD-defined synovitis.
These findings suggest that “[s]wollen joints [are] the better proxy for US synovitis,” and “add to the understanding of how clinical examination relates to underlying pathologies on US imaging which may help to improve the management of early PsA,” write Marzo-Ortega and team in Rheumatology Advances in Practice.
They note, however, that the presence of subclinical synovitis in the study “remains a significant finding,” which is “consistent with the known reduced sensitivity of clinical examination and the disparity reported for clinical and US outcomes.”
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