Clinical Implications of the Age Threshold in the 2022 ACR/EULAR Classification Criteria for Takayasu Arteritis: A Real-World Study of Patients Aged over 61 Years

Background/Objectives: The age item of the 2022 American College of Rheumatology (ACR) and the European Alliance of Associations for Rheumatology (EULAR) criteria for Takayasu arteritis (TAK) (the 2022 ACR/EULAR criteria) limits the reclassification of TAK among patients aged over 61 who were classified as TAK according to the 1990 ACR criteria. Therefore, we evaluated the clinical significance of the age item of the 2022 ACR/EULAR criteria. Methods: We included 22 previously TAK-diagnosed patients aged over 61 (TAK patient aged >61 years) and 41 TAK-reclassified patients aged 50–60 (controls) in this study and retrospectively reviewed their medical records. We compared the satisfied items of the 2022 ACR/EULAR criteria between the two groups and further investigated whether these 22 TAK patients aged >61 years fulfilled the criteria for other relevant diseases. Results: In terms of absolute requirements, TAK patients aged >61 years were significantly older than TAK-reclassified patients aged 50–60. However, there were no further significant differences in the additional clinical and imaging criteria between the two groups. TAK patients aged >61 years exhibited a significantly higher frequency of ascending aorta involvement than TAK-reclassified patients aged 50–60 (18.2% vs. 0%, p = 0.012). Among the 22 TAK patients aged >61 years, ten were categorized as clinically isolated aortitis, and three of the ten patients with CIA could additionally be categorized as restrictively defined-isolated aortitis. Conclusions: Our findings support the need for external validation of the current age threshold in larger cohorts from different ethnic and geographical populations.