Twin international studies unveil the first validated scoring tool and definition for enthesitis.
Two landmark international studies presented at ACR Convergence 2025 could redefine how clinicians detect and classify enthesitis – a key and often early feature of psoriatic arthritis – using ultrasound.
Together, the findings mark a significant advance toward precision imaging and standardised assessment in PsA diagnosis, with potential to improve early detection, clinical decision-making, and the design of future trials.
The first study a poster presentation titled The Development and Validation of a Diagnostic Ultrasound Enthesitis Score (DUET) for Psoriatic Arthritis, introduced a novel scoring system designed to improve the accuracy of PsA diagnosis.
The DUET tool, developed across 17 global centres, uses standardised ultrasound imaging of 16 entheseal sites to differentiate PsA from other musculoskeletal conditions. The validation cohort demonstrated strong diagnostic performance, with age-stratified models enhancing accuracy further.
It was led by Dr Lihi Eder, rheumatologist and clinician-scientist at Women’s College Hospital, University of Toronto.
The second study, Defining Sonographic Enthesitis in Psoriatic Arthritis: Developing a Data- and Expert-Driven Definition for Inflammatory Enthesitis at the Single Enthesis Level, aimed to address a critical gap in rheumatology – the lack of a validated definition for inflammatory enthesitis at the individual site level.
The presenting author was Dr Andre Lucas Ribeiro, a rheumatologist at Hospital de Clínicas de Porto Alegre & Hospital Moinhos de Vento in Brazil, and PhD Candidate at Universidade Federal do Rio Grande do Sul.
Using expert consensus and quantitative analysis of 90 ultrasound scans, researchers established a robust framework for identifying definite inflammatory enthesitis, aiming to reduce misclassification and improve patient selection for clinical trials.
“These studies represent a leap forward in precision imaging for PsA,” said Dr Eder.
“By standardising how we define and score enthesitis, we can diagnose earlier, treat more effectively, and ultimately improve patient outcomes.”
DUET: A GLOBAL EFFORT TO BUILD A RELIABLE DIAGNOSITIC TOOL
Enthesitis – inflammation at the sites where tendons or ligaments attach to bone – is a hallmark of PsA and can often precede joint inflammation.
While musculoskeletal ultrasound (MSK-US) is highly sensitive in detecting these changes, its diagnostic use in PsA has been hampered by the lack of a validated, disease-specific scoring framework, the researchers noted in their poster.
To address this, the DUET study brought together 17 international centres across North America, Europe, and the Middle East. Researchers enrolled more than 400 participants, including patients with early PsA, psoriasis without arthritis, and non-inflammatory musculoskeletal controls.
Each participant underwent detailed ultrasound imaging at 16 entheseal sites across the upper and lower limbs.
Images were centrally reviewed by three expert readers, and a wide range of inflammatory and structural lesions were scored – including hypoechogenicity, thickening, power Doppler (PD) activity, calcification, enthesophytes, and erosions.
Using a stepwise statistical model and age-stratified logistic regression, the team identified combinations of lesions and anatomical sites that best discriminated PsA from controls. The final DUET score incorporated both inflammatory and structural components, specifically inflammatory and structural.
These were measured at three key sites: the Achilles tendon, patellar tendon (patellar insertion), and triceps tendon.
The score showed strong diagnostic performance in both discovery and validation cohorts, achieving specificity between 73% and 100% and sensitivity up to 63% among patients with tender entheses.
Moreover, DUET scores correlated with overall disease activity and were elevated among patients about to escalate PsA therapy.
“DUET is a newly developed sonographic tool that may assist in the diagnosis of PsA, particularly among individuals with tender entheseal sites,” the researchers concluded.
TOWARDS A STANDARD DEFINITION OF INFLAMMATORY ENTHESIITIS
The other study, presented at a session on spondyloarthritis Including PsA tackled another long-standing problem in rheumatology – the lack of a validated, site-level definition for inflammatory enthesitis.
While the OMERACT group has standardised descriptions for ultrasound-detectable lesions, no consensus has existed for what specifically constitutes definite inflammatory enthesitis, the researchers said.
“This limits diagnostic specificity and contributes to misclassification and overtreatment,” they wrote in their abstract.
To address this, the DUET expert panel – comprising 10 experienced sonographers from across the DUET network – independently reviewed 90 ultrasound video scans of PsA patients, covering six entheseal sites.
Each expert rated scans from “definite not inflammatory enthesitis” (-10) to “definite inflammatory enthesitis” (+10).
Consensus was reached in 70% of cases, allowing researchers to quantitatively link specific sonographic features with expert agreement. Nearly all “definite” cases displayed a power Doppler (PD) signal of grade 2 or higher near the bone cortex, typically accompanied by hypoechogenicity and/or thickening.
Isolated structural findings, such as small enthesophytes, were deemed insufficient for diagnosis unless present within a broader inflammatory pattern. Structural lesions like erosions and cortical irregularities were interpreted as signs of prior, not active, inflammation.
Based on this analysis and a subsequent Delphi consensus vote, the team proposed a formal definition of inflammatory enthesitis:
“Inflammatory enthesitis is defined as the presence of a power Doppler signal grade ≥2 near the bone cortex, in the presence of hypoechogenicity and/or thickening of the entheseal structure, and within the appropriate clinical context.”
This definition excluded cases where findings were better explained by factors such as mechanical stress or trauma. The researchers noted that the final definition achieved a 100% consensus from the 10 expert sonographers.
Dr Ribeiro told the conference that the results had implications for patients as well as researchers.
“We propose this new definition, with a strong focus on specificity over sensitivity, to be used for clinical trials and research in general, to be sure that we are really enrolling the correct patient into the correct trial, and the patient that really might benefit the most to being exposed to that therapy,” he said.
A STEP TOWARDS PRECISION RHEUMATOLOGY
Together, the DUET scoring system and new definition for inflammatory enthesitis mark a transformational moment for imaging in PsA.
By providing both a quantitative tool and a qualitative framework, these studies lay the groundwork for consistent, reproducible ultrasound evaluation across research centres and clinical settings worldwide.
For clinicians, the impact could be immediate, in the form of earlier diagnosis, better disease stratification, and more targeted treatment decisions.
For researchers, it opens the door to standardised patient selection and endpoint assessment in upcoming PsA trials, accelerating the path toward precision rheumatology.
This content has been independently prepared by Rheumatology Republic with education funding from UCB Australia Proprietary Limited. The views expressed do not necessarily reflect the views of UCB Australia. AU-BK-2500275
