Diagnostic, research, and real-life effect of the 2023 EULAR−ACR classification criteria for antiphospholipid syndrome

The role of classification criteria is particularly important in rheumatic diseases compared with other medical disorders, as the complexity and overlapping symptoms of these conditions make diagnosis challenging. Moreover, the absence of established diagnostic criteria further complicates diagnosing patients. Classification criteria can assist health-care professionals and patients as a diagnostic aid. However, classification criteria are developed for research purposes to standardise populations in clinical trials and observational studies of rheumatic diseases and not for diagnosing patients. Introduction of the 2023 American College of Rheumatology−European Alliance of Associations for Rheumatology (ACR–EULAR) antiphospholipid syndrome classification criteria underscores the important distinction between meeting these criteria and being diagnosed with the condition—a differentiation essential in both clinical practice and research. Although the 2023 ACR–EULAR antiphospholipid syndrome classification criteria improved precision in classification of pregnant individuals with antiphospholipid syndrome, which ultimately should lead to better outcomes and care for these patients, the updated criteria should not be used as diagnostic criteria in routine clinical practice. In this Personal View, we examine the possible effect of the 2023 ACR–EULAR antiphospholipid syndrome classification criteria, with a particular focus on the pregnancy-related aspects of the syndrome.