Systemic lupus erythematosus laboratory tests
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Differentiating Systemic lupus erythematosus from other Diseases |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: {{MIR}
Overview
- An elevated/reduced concentration of serum/blood/urinary/CSF/other [lab test] is diagnostic of [disease name]
- OR
- Laboratory findings consistent with the diagnosis of [disease name] include [abnormal test 1], [abnormal test 2], and [abnormal test 3].
Some patients with [disease name] may have elevated/reduced concentrations of [test], which is usually suggestive of [progression/complication].
Laboratory tests
| Lab exam | result | clinical correlation | ||
|---|---|---|---|---|
| Hematology | Complete blood count | leukopenia
mild anemia thrombocytopenia |
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| serum creatinine | Elevated | suggestive of renal dysfunction | ||
| Urinalysis with urine sediment | hematuria, pyuria, proteinuria, and/or cellular casts | |||
| Serology | ANA | positive in virtually all patients with SLE at some time in the course of their disease | If the ANA is positive, one should test for other specific antibodies such as dsDNA, anti-Sm, Ro/SSA, La/SSB, and U1 ribonucleoprotein (RNP) | |
| Antiphospholipid antibodies | lupus anticoagulant [LA], IgG and IgM anticardiolipin [aCL] antibodies; and IgG and IgM anti-beta2-glycoprotein [GP] | |||
| complement levels | C3 and C4 or CH50 | |||
| Erythrocyte sedimentation rate (ESR) | ||||
| C-reactive protein (CRP) | ||||
| Urine protein-to-creatinine ratio | ||||
| Anti-dsDNA | highly specific for SLE
in 70% of patients |
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| anti-Sm antibodies | highly specific for SLE
lack sensitivity in 30% of patients |
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| Anti-Ro/SSA antibodies | in 30% of patients
more commonly associated with Sjögren’s syndrome 15593352 |
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| anti-La/SSB antibodies | in 20% of patients
more commonly associated with Sjögren’s syndrome 15593352 |
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| Anti-U1 RNP antibodies | in approximately 25 percent of patients with SLE
Not specific, always present in patients with mixed connective tissue disease (MCTD) 15593352 |
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| Antiribosomal P protein antibodies | high specificity for SLE & low sensitivity for SLE
lack specificity for involvement of a particular organ system or disease manifestation. |
If the initial ANA test is negative, but the clinical suspicion of SLE is high, then additional antibody testing may still be appropriate. This is partly related to the differences in the sensitivity and specificity among the methods used to detect ANA.
Laboratory exams to distinguish SLE from other diseases
| anti-cyclic citrullinated peptide (CCP) antibodies | In patients with predominant arthralgias or arthritis may help exclude a diagnosis of rheumatoid arthritis (RA)
higher specificity for RA and may be more useful for distinguishing the arthritis associated with RA. (See "Biologic markers in the diagnosis and assessment of rheumatoid arthritis", section on 'Rheumatoid factors' and "Biologic markers in the diagnosis and assessment of rheumatoid arthritis |
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| Rheumatoid factor (RF) | less diagnostic utility since 20 to 30 percent of people with SLE have a positive RF | ||
| Serological studies for infection | serologic testing for human parvovirus B19 | In patients with a brief history (for example, less than six weeks) of predominant arthralgias or arthritis | |
| serologic testing for hepatitis B virus (HBV) and hepatitis C virus (HCV) | in patients with multisystemic clinical findings | ||
| serologic studies for Borrelia | n areas endemic for Lyme disease | ||
| Testing for Epstein-Barr virus (EBV) | |||
| Creatine kinase (CK) | may reflect myositis, which is relatively uncommon in patients with SLE. | Myositis may also suggest an alternative diagnosis such as MCTD, polymyositis (PM), or dermatomyositis (DM). |