New classification criteria for systemic lupus represent a “paradigm shift” in how the disease is diagnosed and studied, its developers say.

The 2019 criteria from the American College of Rheumatology (ACR) and the European League Against Rheumatism (EULAR) require an antinuclear antibody (ANA) titre of at least 1:80 on HEp-2 cells or an equivalent positive test at least once.

If absent, the patient is considered not to have SLE. If present, 22 “additive weighted” classification criteria are considered.

They are clustered into seven separate clinical domains (constitutional, haematological, neuropsychiatric, mucocutaneous, serosal, musculoskeletal and renal), and three different immunological domains (antiphospholipid antibodies, complement proteins and SLE-specific antibodies).