EULAR develops new disease activity score for antiphospholipid syndrome

EULAR - The European Alliance of Associations for Rheumatology - has developed a new disease activity score that quantifies the level of disease activity in people with antiphospholipid syndrome (APS). It awaits prospective validation, but could be useful to help measure activity as opposed to severity - tracking symptoms over time, both in clinical trials and in everyday practice.

APS is a systemic autoimmune disorder. It is characterised by the presence of antiphospholipid antibodies and a broad spectrum of clinical features, causing obstetric as well as thrombotic, microvascular and non-thrombotic (TMN) symptoms. These can range in severity, and people may have involvement at only one or multiple sites. Increasing evidence suggests that APS might be driven by an interplay between both thrombotic and inflammatory mechanisms.

In 2023, EULAR worked with the American College of Rheumatology to develop classification criteria for APS, which focused on five key domains. But in addition to these, a disease activity score that assesses different clinical manifestations would be useful to help evaluate people's response to treatment in clinical trials, as well as for monitoring disease in observational studies and clinical practice.

Of note, the concept of disease activity is separate from severity, which reflects aspects of both current activity and accumulated damage - and its impact on health, function, quality of life, and prognosis. Instead, disease activity refers to new-onset events such as a new venous thromboembolism, or the improvement of thrombocytopenia after treatment.

To address this, EULAR set out to develop and validate a new disease activity score, which they have called EAPSDAS. The task force included healthcare professionals and patient research partners. The project initially generated 170 items, and after removing duplicates, 140 were rated, with a final 30 passing the voting threshold for consensus. Of these, 24 items are included in the new EAPSDAS TMN scale, and 6 items in the obstetric scale. Separate stand-alone scores have been defined for these two domains because combining them would bias the results against anyone who is not pregnant. Additionally, the tool has been designed as a scale rather than an index, since some APS manifestations are episodic, whereas others are more continuous.

To use the EAPSDAS, the observation time for the TMN scale is divided into monthly intervals, with the highest-rated score achieved for each patient in any monthly interval over the entire observation time is defined as the maximum score. The average of each monthly score over the observation time is defined as the average TMN score. The maximum score gives an indication of the highest or peak level of activity, while the average score provides an indication of the persistence. For the obstetric scale there is no average since only a single event may occur.

Given that new treatment targets and potential novel agents are emerging in APS, the development of EAPSDAS will help enable well-designed clinical trials for new treatments in people living with APS. Using EAPSDAS as a primary outcome in future clinical trials for new treatments of the thrombotic, obstetric, microvascular (such as APS nephropathy), and non-thrombotic (such as thrombocytopenia or cardiac valve disease) APS manifestations will help evaluate disease activity status and response to therapy".

Professor Maria Tektonidou, lead author on the paper and Head of the Rheumatology Unit at the First Department of Propaedeutic Internal Medicine, National and Kapodistrian University of Athens, Athens, Greece

Using data-driven and consensus methodology, EAPSDAS was developed, and initial validation was performed. Further validation in prospective studies is warranted, but EULAR hopes the new EAPSDAS can be used to evaluate APS activity in trials of new treatments.