WASHINGTON — New draft guidance on the use of musculoskeletal ultrasound (MSUS) for diagnosis, monitoring, and prognosis of psoriatic arthritis was presented at the American College of Rheumatology (ACR) 2024 Annual Meeting. The new recommendations, intended to update 2012 guidance on rheumatologic use of MSUS, will go through another round of expert committee voting before being finalized and published.
"Even in the last 12 years, we've seen substantive advances, and there's been significant improvements in musculoskeletal ultrasound technology," Veena K. Ranganath, MD, a professor of clinical medicine at the University of California, Los Angeles, and director of their Rheumatology Fellowship Musculoskeletal Ultrasound Training Program, told attendees. She noted that more than 30,000 articles on MSUS and arthritis have been published since the 2012 guidance. "We've seen mastery in teaching and really a wide distribution of this education to the next generation of dermatologists, and this has led to significant increases in the use of musculoskeletal ultrasound in clinical practices."
She also noted there have been significant improvements in therapeutic agents and strategies in psoriatic arthritis medications and that differences in today's patients compared with those of a decade ago have influenced clinical questions related to the use of MSUS in rheumatology.
To develop the guidelines, a committee identified key domains and relevant clinical questions for ultrasonography using the PICO model (patient/population, intervention, comparison, and outcomes). A review of the literature published since 1993 in PubMed, Embase, and the Cochrane Database provided the evidence base, and a committee of 11 experts voted on the strength of the evidence for 22 statements. They rejected two that lacked consensus, and another round of voting will occur before the guidance is published.
Michael Stein, MD, an assistant professor of medicine in rheumatology at McGill University in Montreal, Quebec, Canada, who was not involved in the guidance development, said he hopes and expects this new guidance will help persuade more clinicians to recognize the value of using MSUS in their practice.
"Number one, it'll highlight the huge amount of data that exist that support using this technology for managing these groups of patients, among others, and I think it'll also highlight the enormous number of questions that still exist that will hopefully be answered in the future, promoting new research," Stein told Medscape Medical News.
"I do think it does allow people who are not comfortable with technology to adopt technology in a very gradual way and make it less threatening," Stein added.
"Ultrasound is becoming part of the landscape, and so increasingly, we're trying to promote it as being part of the standard of care, or at least an adjunct to care. I commend the committee for doing all this amazing work."
Predicting and Diagnosing Early Psoriatic Arthritis
Catherine Bakewell, MD, a rheumatologist at Intermountain Health in Salt Lake City, Utah, reviewed the committee's statements, starting with strong consensus that MSUS can help with diagnosing early psoriatic arthritis. Evidence has shown that patients with psoriasis who have subclinical synovitis, enthesitis, and other features have gone on to develop psoriatic arthritis, and researchers have documented the transition with ultrasonography.
"We can use it to enhance our CASPAR classification criteria" by using ultrasound to change how clinicians apply the classification criteria, Bakewell said. "For example, in order to go through those classification criteria, a patient has to have confirmed inflammatory articular disease, either the joint synthesis or spine, and ultrasound can help clarify that state for us."
She also noted the potential for ultrasonography to help as a screening tool because studies have suggested that dermatologists' use of handheld ultrasound transducers can help in screening appropriate patients to refer to rheumatologists.
Patients with psoriasis being evaluated for a potential early psoriatic arthritis diagnosis should undergo MSUS of the bilateral quadriceps tendon, patellar ligament, Achilles tendon, and plantar fascia entheses at a minimum, per moderate consensus.
"This truly is just designed to be the highest bang for your buck. This is designed for clinicians in practice," Bakewell said. She noted criticism about the exclusion of upper extremities — something that will be discussed in the future published paper — but one reason that was excluded is because common findings have occurred in healthy individuals in some areas.
Moderate consensus also supported reliance on entheseal features — including hypoechogenicity, thickening, Doppler signal, bone erosions, enthesophytes/calcifications, and bursal enlargement — to support a diagnosis. Interpretation of entheseal changes in patients with psoriasis should take into account characteristics such as age, body mass index (BMI), and biomechanical stress.
"There are numerous articles already existing pointing out that people who are over the age of 50 with a BMI over 30 kg/m2 or who have higher levels of biomechanical stress will score more highly on endocytoscoring systems, even in the absence of an underlying disorder," Bakewell said. Among the mitigating strategies proposed in the literature are to have at least three positive sites to qualify for an indication or to look at the specificity of each elementary lesion. "Whatever mitigating strategy the clinician chooses to use, they need to bear in mind some of these features are not exclusive to spondyloarthritis," she said. "It has to be taken in the clinical context."
Scanning the hand, wrist, foot, and relevant symptomatic joints with MSUS to diagnose early psoriatic arthritis in patients with psoriasis received strong consensus. Intracapsular findings of synovitis and erosions may help support an early diagnosis in patients with psoriasis. "These are not obviously specific to psoriatic arthritis but support the diagnosis" with moderate consensus, Bakewell said. "The more specific findings are these extracapsular findings — which did attain a strong level of consensus — which are enthesitis, tenosynovitis, and dactylitis, all supporting that diagnosis of early psoriatic arthritis."
For patients with psoriatic arthritis, the cutoff for defining a positive joint received moderate consensus for grayscale (GS) of at least 2 or at least 1 with power Doppler (PD) of at least 1.
Strong consensus supported confirming the presence of dactylitis in patients with psoriasis or psoriatic arthritis through a combination of features including tenosynovitis, subcutaneous edema, soft tissue thickening, synovitis, paratenonitis, and pulley thickening.
"I will also note that enthesitis is missing from this definition of dactylitis," Bakewell said. "It is, however, a feature that is detectable with those higher-frequency transducers, but this is a relatively early area of research and did not make it into this guidance statement."
Moderate consensus supported determination of an increased risk of radiographic erosions in patients with a dactylitis PD score of at least 1.
"We know as far back as 2005, Brockbank et al taught us that the dactylitic digit is associated with radiographic erosion in that particular digit," Bakewell said. "Flash forward all the way to 2021: Dubash et al published the paper, 'Dactylitis is an indicator of a more severe phenotype independently associated with greater swollen joint counts, C-reactive protein, ultrasound synovitis, and erosive damage,' showing us that this is more than just that particular digit. It is a more severe phenotype, and very minimal Doppler signal, just 1+, is associated with erosive damage."
Progression of Psoriatic Arthritis and Shared Decision-Making
Strong consensus existed for all statements related to progression of psoriatic arthritis and the role of MSUS in shared decision-making. The first is that synovitis and enthesitis in MSUS can predict radiographic progression and worsening of patient-related outcomes. Second, sonographic features — including increased Doppler signal in synovitis, enthesitis, and tenosynovitis — and presence of bone erosions and dactylitis can help inform decisions regarding therapy escalation.
"This is the first treatment management–specific statement we have made, but we feel this to be justified because each of these ultrasonographic features is associated with overall inflammatory burden and worse outcomes, be it health assessment questionnaires, disability index, or patient-reported outcomes to harder endpoints, such as radiographic erosions or relapse of clinical remission," Bakewell said.
Finally, MSUS can help inform patients of their disease activity to assist in shared decision-making regarding escalation or de-escalation of therapy.
"We've all had this in our practices. You've had the patient in front of you who is very inflamed, and they say, 'Doctor, can't I please use doTERRA oils? Do I really need to go on one of these toxic drugs? I've read the package insert,'" Bakewell said. "Aside from having that conversation about the relative risk–benefit of any individual medication that you recommend, it's helpful to put the ultrasound transducer on the patient, show them the fire of the Doppler, show them the erosion, show them the damage that is being done. It comes to life for them, especially if they're not suffering that much with pain or stiffness."
Bakewell also addressed patients at the other end of the pain spectrum who are suffering more. "You've also probably had the patient with psoriatic arthritis and fibromyalgia who comes in and tells you, 'Doctor, my psoriatic arthritis has been terrible. I'm flaring. I need more immune-suppressing medication,'" she said. "Their exam looks pretty good, and it's helpful to put that transducer on them and show them the absence of Doppler signal, show them that you're taking them very seriously. You didn't just squeeze them and say they're fine, but you looked more deeply. You looked underneath the skin, and that helps with that patient–provider understanding and communication. I use this every day."
Clarifying Disease State and Defining Remission
As with patients with psoriasis undergoing evaluation, there was strong consensus for interpreting entheseal changes in psoriatic arthritis in the context of patient characteristics such as age, BMI, and biomechanical stress.
There was moderate consensus for confirming psoriatic arthritis flare with MSUS. Bakewell noted that many have seen in their practices how physical exams can be misleading, such as when a patient appears clinically normal but has ongoing synovitis, or on the flip side, the patient has a swollen joint but nothing is lighting up with Doppler on the ultrasound.
All of the statements on MSUS for remission received moderate consensus. These included defining MSUS remission as a PD score of 0 in entheses and synovial tissues and defining ultrasonographic remission as a total PD ultrasound score of 0, summing all analyzed joints and entheses, at a single given time point.
When using MSUS to evaluate for remission, it's reasonable to screen the lower-extremity entheses, wrists, metacarpophalangeal joints, interphalangeal hand joints, metatarsophalangeal joints, and relevant symptomatic joints. The inflammatory features to evaluate to confirm ultrasound-defined remission include PD enthesitis, GS and PD synovitis, tenosynovitis, and dactylitis. Finally, for those in remission, subclinical inflammation detected by MSUS likely predicts a higher rate of flare.
During the discussion, Bakewell reiterated that MSUS should be regarded as a tool for patient subsets who can benefit from its use, rather than being used routinely across large patient groups without a clear purpose. "It's used to answer a question," she said. "If you're going to demonstrate the efficacy of a tool, you have to use it appropriately, aka when there's a question. We don't need to ultrasound every patient every visit."
No external funding for the development of the guidance was noted. Ranganath has reported receiving research support from Bristol Myers Squibb and Mallinckrodt. Bakewell has reported receiving speaking/consulting fees from AbbVie, UCB, Lilly, Janssen, Novartis, Sanofi/Regeneron/Genzyme, and Pfizer. Stein had no disclosures.
Tara Haelle is a Dallas-based science/health journalist.