diagnostic criteria in SLE, presented in the "SOAP BRAIN MD" acronym:
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Serositis - Pleurisy, pericarditis on examination or diagnostic ECG or imaging
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Oral ulcers - Oral or nasopharyngeal, usually painless; palate is most specific
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Arthritis - Nonerosive, two or more peripheral joints with tenderness or swelling
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Photosensitivity - Unusual skin reaction to light exposure
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Blood disorders - Leukopenia (< 4 X 103 cells/µL on more than one occasion), lymphopenia (< 1500 cells/µL on more than one occasion), thrombocytopenia (< 100 X 103 cells/µL in the absence of offending medications), hemolytic anemia
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Renal involvement - Proteinuria (>0.5 g/d or 3+ positive on dipstick testing) or cellular casts
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ANAs - Higher titers generally more specific (>1:160); must be in the absence of medications associated with drug-induced lupus
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Immunologic phenomena - dsDNA; anti-Smith (Sm) antibodies; antiphospholipid antibodies (anticardiolipin immunoglobulin G [IgG] or immunoglobulin M [IgM] or lupus anticoagulant); biologic false-positive serologic test results for syphilis, lupus erythematosus (LE) cells (omitted in 1997)
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Neurologic disorder - Seizures or psychosis in the absence of other causes
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Malar rash - Fixed erythema over the cheeks and nasal bridge, flat or raised
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Discoid rash - Erythematous raised-rimmed lesions with keratotic scaling and follicular plugging, often scarring
In patients with high clinical suspicion or high ANA titers, additional testing is indicated. This commonly includes evaluation of antibodies to dsDNA, complement, and ANA subtypes such as Sm, SSA, SSB, and ribonucleoprotein (RNP) (often called the ENA panel). Screening laboratory studies to diagnose possible SLE should include a CBC count with differential, serum creatinine, urinalysis with microscopy, ANA, and, perhaps, basic inflammatory markers. The following are autoantibody tests used in the diagnosis of SLE:[24]
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ANA - Screening test; sensitivity 95%; not diagnostic without clinical features
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Anti-dsDNA - High specificity; sensitivity only 70%; level variable based on disease activity
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Anti-Sm - Most specific antibody for SLE; only 30-40% sensitivity
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Anti-SSA (Ro) or Anti-SSB (La) - Present in 15% of patients with SLE and other connective-tissue diseases such as
Sjögren syndrome; associated with
neonatal lupus -
Anti-ribosomal P - Uncommon antibodies that may correlate with lupus cerebritis
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Anti-RNP - Included with anti-Sm, SSA, and SSB in the ENA profile; may indicate mixed connective-tissue disease with overlap SLE,
scleroderma, and myositis
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Anticardiolipin - IgG/IgM variants measured with enzyme-linked immunoassay (ELISA) among the antiphospholipid antibodies used to screen for antiphospholipid antibody syndrome
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Lupus anticoagulant - Multiple tests (eg, Direct Russell Viper Venom test) to screen for inhibitors in the clotting cascade in antiphospholipid antibody syndrome
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Coombs test - Coombs test–positive anemia to denote antibodies on RBCs
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Anti-histone - Drug-induced lupus ANA antibodies often this type (eg, with procainamide or hydralazine; perinuclear antineutrophil cytoplasmic antibody [p-ANCA]–positive in minocycline-induced drug-induced lupus)
Other laboratory tests used in the diagnosis of SLE include the following:
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Inflammatory markers: Levels of inflammatory markers, including the erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP), may be elevated in any inflammatory condition, including SLE. CRP levels change more acutely, and the ESR lags behind disease changes.
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Complement levels: C3 and C4 levels are often depressed in patients with active SLE because of consumption by immune complex–induced inflammation. In addition, some patients have congenital complement deficiency that predisposes them to SLE.
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A CBC count may help to screen for leukopenia, lymphopenia, anemia, and thrombocytopenia, and urinalysis and creatinine studies may be useful to screen for kidney disease.
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Liver test results may be mildly elevated in acute SLE or in response to therapies such as azathioprine or nonsteroidal anti-inflammatory drugs (NSAIDS).
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Creatinine kinase levels may be elevated in myositis or overlap syndromes.
