Table 9-2 lists the classification criteria developed by an international SLE study group. Although this schema is intended primarily for research purposes, clinicians have found it useful in diagnosing and documenting the disease. Patients must satisfy at least 4 of the 17 criteria, including at least 1 clinical and 1 immunologic criterion. Alternatively, SLE can be diagnosed in patients with biopsy-proven nephritis with positive ANA or anti–double-stranded DNA (anti-dsDNA) antibodies. More recently, the British Society for Rheumatology released new UK-based guidelines for the diagnosis, assessment, and treatment of nonrenal manifestations of SLE (referenced in the Treatment section).
ANA testing should be ordered for suspected cases of SLE, as virtually all patients with SLE have positive titers of 1:160 or higher. Lower ANA titers limit the test specificity, as up to a third of unaffected individuals have a titer of 1:40. Thus, testing should be reserved for cases of high clinical suspicion. Three other immunologic tests that are highly specific for SLE are anti-dsDNA, anti-Smith (anti-Sm), and antiphospholipid antibodies. The presence of any 1 of these is considered an acceptable immunologic criterion. Additionally, antiribosomal P protein antibodies have a high specificity and can be helpful when the diagnosis is uncertain. Several other autoantibodies (anti-Ro/SS-A, anti-La/SS-B, anti-RNP, and anti-RA33) may indicate a predisposition to SLE or other autoimmune disease, but they are not included within the classification system.
Table 9-2 SLICC Criteria for Diagnosis of Systemic Lupus Erythematosus
Excerpted from BCSC 2020-2021 series: Section 1 - Update on General Medicine. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.