Tests
Diagnosis is made by, clinical evaluation of patient symptoms and examination findings, as well as the results of investigations. The following laboratory tests may be useful in the diagnosis of SLE:

• Testing for autoantibodies:
Anti-nuclear antibody test (ANA) is positive in almost all patients with SLE
anti-double stranded DNA antibodies are frequently present, and the level can fluctuate with disease activity
anti-Sm (specific to lupus, but only seen in 10-30% of cases)
anti-SSA (Ro) and anti-SSB (La) antibodies may also be positive
antiphospholipid antibodies

• Urine analysis– may show blood, microscopic casts of kidney cells, or protein
• Full blood count (FBC) – decrease in some cell types, including platelets
• Serum protein electrophoresis – increased immunoglobulins
• Erythrocyte sedimentation rate (ESR)  – increased
• C-reactive protein (CRP) is typically normal, unless coexistent infection is present
• Complement 3 (C-3) – may be decreased; the level can fluctuate with activity of the disease