Systemic Lupus Erythematosus Diagnosis and Management

Diagnostic Criteria

The American College of Rheumatology suggests that a positive ANA at 1:320, which exceeds the diagnostic threshold, makes SLE highly likely when combined with clinical features, with optimal specificity of 86.2% and sensitivity of 95.8% for systemic autoimmune rheumatic diseases 1
Cytopenias, including anemia, leukopenia, and thrombocytopenia, are characteristic of SLE, with anemia having a hemoglobin level of 89 g/L, leukopenia having a white blood cell count of 3.2 x 10⁹/L, and thrombocytopenia having a platelet count of 99 x 10⁹/L 2, 3

The presence of a ferritin level of 920 pg/L, which is elevated but far below the typical range for AOSD, argues against Adult-Onset Still's Disease (AOSD), as AOSD typically presents with ferritin levels >1000 ng/mL 4, 2
The absence of a characteristic salmon-pink, evanescent rash on the trunk and the absence of a quotidian fever pattern also argue against AOSD 2, 3

The European League Against Rheumatism recommends testing for anti-dsDNA antibodies, which are highly specific for SLE, using the Crithidia luciliae immunofluorescence test for highest specificity 1
Testing for anti-Smith (Sm) antibodies, which are highly specific for SLE with strong confirmatory power, is also recommended 1
A urinalysis with microscopy to evaluate for lupus nephritis (proteinuria, cellular casts) is necessary 1