Development and validation of a EULAR disease activity score in antiphospholipid syndrome

Objectives: To develop and validate a European Alliance of Associations for Rheumatology (EULAR) disease activity score in antiphospholipid syndrome (EAPSDAS). Methods: Twenty-four Task Force members and an international group of 53 antiphospholipid syndrome (APS) experts/collaborators, 65 patients with primary APS, and 21 healthcare professionals participated. EAPSDAS development proceeded in 4 phases: (i) item generation using a systematic literature review and 2 surveys; (ii) item reduction by rating items on their importance to be included in EAPSDAS and using Delphi methodology; (iii) item scoring based on real-world clinical vignettes and using as criterion standard the physician global assessment (PhysGA); and (iv) validation. Results: One hundred seventy items representing APS activity were generated, and 140 deduplicated candidate items were rated by participants. Using a ≥75% vote threshold and Delphi consensus among Task Force members, 24 items were included in the EAPSDAS thrombotic/microvascular/nonthrombotic (TMN) scale and 6 in the obstetric scale. Item scoring was based on ratings of 3 versions of 60 vignettes with new/worsening manifestations (30 single TMN or obstetric manifestations, 26 combinations of 2 TMN manifestations, 2 inactive cases, 2 testing cases) by physicians. Item scores were calculated as the adjusted mean PhysGA in linear regression analysis. A 1-month time frame was defined for the TMN scale and the entire pregnancy for the obstetric scale. Scores for stable or improved TMN manifestations were also included. High face and content validity, construct validity (internal/external standard), and reliability were demonstrated using real-world clinical vignettes. Conclusions: Using data-driven and consensus methodology, EAPSDAS was developed and initial validation was performed. Further validation in prospective studies is warranted.