EULAR develops new classification criteria for hand osteoarthritis

At present, classifying hand osteoarthritis (OA) is based on clinical findings, and available tools are not able to distinguish between certain phenotypes. With new disease-modifying treatments in development, trials will require reliable classification criteria to ensure accurate comparisons between groups. To support this, EULAR – The European Alliance of Associations for Rheumatology – has developed new classification criteria for hand OA.

Hand osteoarthritis mainly affects the distal interphalangeal, proximal interphalangeal, and thumb base joints, leading to joint pain, aching, and stiffness. Criteria developed by the American College of Rheumatology (ACR) in 1990 are useful, but they cannot distinguish between interphalangeal or thumb base disease, and this is important since these two phenotypes may require different treatment strategies.

To address this, EULAR and a team of leading experts in the field set out to develop new classification criteria sets that include radiographic features. Early phases of the project used observational data to identify self-reported, clinical, radiographic, and laboratory features associated with OA in the hand. This information was then subjected to a consensus-driven decision-making approach to refine the criteria and determine their relative importance. Now, EULAR report on the third phase of the project to determine the optimal cut-off for disease classification, and test sensitivity and specificity of the proposed criteria.

The new work, published in the May 2024 issue of the Annals of the Rheumatic Diseases, suggests that - in people with symptoms and no other relevant disease or acute injury - hand osteoarthritis can be classified based on age, duration of morning stiffness, number of joints with osteophytes and joint space narrowing, and agreement between symptoms and X-ray findings. This new approach allows researchers to apply the criteria in large studies without needing to perform additional clinical joint examinations. The new system gives a score for each element - with overall hand osteoarthritis classified if a person achieves 9 or more points on a total scale of 0-15, or a score of 8 for interphalangeal or thumb base disease, allowing classification of these challenging phenotypes that do not fulfil the criteria for overall hand osteoarthritis.

EULAR hopes that the new classification criteria will enable the inclusion of more homogenous
patient populations in research studies and clinical trials. Crucially, the separate classification criteria for different phenotypes may support the design of clinical trials for targeted interventions. In the meantime, control-group studies are needed for further validation of these criteria.