20th Anniversary

OMERACT continues to set standards on research outcomes, enhancing the patient voice


Clinical research in rheumatology was suffering from an identity crisis of sorts 40 years ago. A lack of consensus across continents resulted in differing views about clinical outcome measures and judgments about treatments.

Patients were not allowed to be the generating source of a clinical outcome, according to Peter Tugwell, MSc, MD. “The only outcomes that were acceptable were clinician assessments, blood tests, and imaging,” said Dr. Tugwell, professor of medicine, epidemiology, and public health at the University of Ottawa (Ont.) and a practicing rheumatologist at Ottawa Hospital.

Clinicians were coming to different conclusions about patient responses to treatment when managing rheumatoid arthritis in clinical practice.

OMERACT sought to address this lack of uniformity. This international group, formed in 1992, leverages stakeholder groups to improve outcome measurement in rheumatology endpoints through a consensus-building, data-driven format.

It was originally known as “Outcome Measures in Rheumatoid Arthritis Clinical Trials,” but its leaders have since broadened its scope to “Outcome Measures in Rheumatology.” Over the years, it has evolved into an international network that assesses measurement across a wide variety of intervention studies. Now 30 years old, the network spans 40 active working groups and has influenced work in patient outcomes across 500 peer-reviewed publications.

The network meets every 2 years to address what is always a challenging agenda, said Dr. Tugwell, one of its founding members and chair. “There’s lots of strong opinions.” Participating in the discussions are individuals from all stages of seniority in rheumatology and clinical epidemiology, patient research partners, industry, approval agencies, and many countries who are committed to the spirit of OMERACT.

“The secret to our success has been getting world leaders to come together and have those discussions, work them through, and identify common ground in such a way that the approval agencies accept these outcome measures in clinical trials,” he added.

“My impression was the founders perceived a problem in the early 1990s and devised a consensus method in an attempt to quantify clinical parameters to define disease activity in rheumatoid arthritis – an important first step to do clinical trials and allow comparisons between them,” said Patricia Woo, CBE, FMedSci, FRCP, emeritus professor of pediatric rheumatology and previous head of the Centre for Paediatric and Adolescent Rheumatology at UCL, London. At that time, even disease definitions varied between the United States and Europe and other parts of the world, said Dr. Woo, who is not a part of OMERACT. “This was especially true for pediatric rheumatology.”

Fusing the continental divide

OMERACT arose from a need to streamline clinical outcome measures in rheumatology. Research papers during the 1980s demonstrated a lack of coherence in managing patients with rheumatoid arthritis in routine practice. In addition, the measures used to define clinical endpoints in clinical trials operated in silos – they were either too specific to a certain trial, overlapped with other concepts, or didn’t reflect changes in treatment.

Approval agencies in Europe and North America were approving only outcomes measures developed by their respective researchers. This was also true of patients they tested on. “This seemed crazy,” Dr. Tugwell said.

Dr. Tugwell was involved in the Cochrane collaboration, which conducts systematic reviews of best evidence across the world that assesses the magnitude of benefits versus harms.

To achieve this goal, “you need to pull studies from around the world,” he said. Maarten Boers, MD, PhD, a rheumatologist (and later professor of clinical epidemiology at Amsterdam University Medical Center) from the Netherlands, spent a year in Ontario, Canada, to train as a clinical epidemiologist. Together, Dr. Tugwell and Dr. Boers began discussing options to develop more streamlined outcome measures.

Dr. Maarten Boers (left) and Dr. Peter Tugwell, founders of OMERACT Courtesy OMERACT

Dr. Maarten Boers (left) and Dr. Peter Tugwell, founders of OMERACT

They initiated the first OMERACT conference in Maastricht, the Netherlands, in 1992. The Food and Drug Administration and European Medicines Agency participated, along with leaders of outcomes measurement in Europe and in North America.

Discussions centered on methods to develop outcomes in a meaningful fashion. During the first meeting, North American and European approval agencies agreed to accept each other’s studies and endpoints and patient reported outcomes.

Agreement was achieved on a preliminary set of outcome domains and measures that later became known as the WHO-ILAR (World Health Organization–International League of Associations for Rheumatology) core set. The set included seven outcome domains: tender joints, swollen joints, pain, physician global assessment, patient global assessment, physical disability, and acute phase reactants, and one additional outcome domain for studies lasting 1 year or more: radiographs of the joints.

“A proactive program was planned to test not only the validity of these endpoints, but also the methods for their measurement. This was the start of a continuing process,” OMERACT members said in a joint statement for this article. Meetings have since taken place every 2 years.

Attendees gathered for a photo at the OMERACT 2018 meeting, the last time that the organization was able to hold its biennial meeting in person. Courtesy OMERACT

Attendees gathered for a photo at the OMERACT 2018 meeting, the last time that the organization was able to hold its biennial meeting in person.

OMERACT accomplishments

OMERACT now requires buy-in from four continents: Asia, Australia, Europe, and North America.

Its leaders have developed an explicit process for gaining endorsement of core outcome domains and instrument measurement sets. To fully capture the possibilities of “what to measure,” i.e., “measurable aspects of health conditions,” OMERACT has developed a framework of concepts, core areas, and outcome domains. The key concepts are pathophysiology (with a core area termed “manifestations/abnormalities”) and impact (with core areas of “death/lifespan,” and “life impact,” and the optional area of “societal/resource use”). An outcome domain defines an element of a core area to measure the effects of a treatment, such as blood markers, pain intensity, physical function, or emotional well-being.

A core outcome domain set is developed by agreeing to at least one outcome domain within one of the three core areas. Subsequently, a core outcome measurement set is developed by agreeing to at least one applicable measurement instrument for each core outcome domain. This requires documentation of validity, summarized under three metrics: truth, discrimination, and feasibility.

OMERACT’s handbook provides tutelage on establishing and implementing core outcomes, and several workbooks offer guidance on developing core outcome domain sets, selecting instruments for core outcome measurement sets, and OMERACT methodology.

All this work has led to widespread adoption.

Approval agencies have accepted OMERACT’s filter and methods advances, which have been adopted by many research groups in rheumatology and among nonrheumatology research groups. Organizations such as the U.S. National Institutes of Health’s National Institute of Neurological Disorders and Stroke have sought its advice.

Its core outcomes have been adopted and used for approval in the great majority of studies on rheumatoid arthritis, Dr. Tugwell said.

Several BMJ articles underscore the influence and uptake of OMERACT’s core outcome set. One 2017 paper, which analyzed 273 randomized trials of rheumatoid arthritis drug treatments on ClinicalTrials.gov, found that the WHO-ILAR arthritis core outcome set was reported in 81% of the studies. “The adoption of a core outcome set has the potential to increase consistency in outcomes measured across trials and ensure that trials are more likely to measure appropriate outcomes,” the authors concluded.

Since the initial 1992 meeting, OMERACT has broadened its focus from rheumatoid arthritis to 25 other musculoskeletal conditions.

For example, other OMERACT conferences have led to consensus on core sets of measures for osteoarthritis and osteoporosis, psoriasis/psoriatic arthritis, psychosocial measures, and a core set of data for cost-effectiveness evaluations.

‘Speed is a limitation’

OMERACT is a bottom-up volunteer organization. It doesn’t represent any official organization of any clinical society. “We’ve not asked to be adopted by the American College of Rheumatology, EULAR [European Alliance of Associations for Rheumatology], or other international organizations,” Dr. Tugwell said. It offers a chance for patients, users, and doers of research to work together to agree on rigorous criteria accepted by the approval agencies and take the necessary time to work things through.

This is not a fast process, usually taking 4-6 years to initiate and establish an outcome domain set, he emphasized. “It would be beneficial to do it faster if we had the resources to meet every year. The fact is we’re a volunteer organization that meets every 2 years.”

Speed is a limitation, he acknowledged, but it’s an acceptable trade-off for doing things correctly.

The group has faced other challenges during the COVID-19 pandemic, pivoting to a virtual format that had benefits and limitations.

In one respect, moving to a virtual meeting increased uptake in participation and voting, Dr. Tugwell said. Patient participants with severe rheumatoid arthritis no longer faced the challenges of travel. “On the other hand, we didn’t have the same opportunity to achieve common ground virtually,” he said. “Where there are strong disagreements, I’m a great believer that people need to know one another. There needs to be relationship building.”

OMERACT’s emerging leader program has been a cornerstone of its in-person meetings, engaging young rheumatologists to interact with some of the leaders of outcome measurement. The virtual format dampened this process somewhat, eliminating those important “café chats” between the stakeholders.

The hope is to bring people face-to-face once more at the next meeting in May 2023. The agenda will focus on relationship building, identifying controversial areas, and bringing younger people to develop relationships, Dr. Tugwell said. OMERACT will retain a virtual option for the worldwide voting, “which will allow for more buy-in from so many more people,” he added.


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