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Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the presence of multiple autoantibodies, inflammatory processes, and organ system involvement. , SLE can be fatal, and early disease recognition, treatment, and monitoring can help to prevent complications. However, diagnosis is complicated by the fact that many symptoms of SLE are nonspecific. In addition, SLE and antiphospholipid syndrome (APS) can present similarly and the two diseases can also overlap. Antinuclear antibody (ANA) testing is useful as an initial screening approach, but is not disease specific. In patients with positive ANA test results, additional serologic testing is generally needed to confirm a diagnosis of SLE. Other laboratory tests are recommended at initial evaluation to help to identify organ involvement. See Laboratory Testing below.
Quick Answers for Clinicians
Presenting symptoms of systemic lupus erythematosus (SLE) are often nonspecific. In addition to arthralgia, myalgia, fatigue, weight loss, and fever, patients may present with malar rash, photosensitivity, pleuritic chest pain, Raynaud phenomenon (new onset), and mouth sores. SLE should be suspected in patients who demonstrate symptoms in two or more of these organ systems: cardiac, constitutional, dermal, gastrointestinal, hematologic, musculoskeletal, neuropsychiatric, pulmonary, renal, or reticuloendothelial.
The American College of Rheumatology (ACR) recommends against performing “subserology” tests, or subsequent testing for autoantibodies such as anti-double-stranded DNA (dsDNA) and anti-Smith, in patients who are negative for antinuclear antibodies (ANAs) and who do not have clinical indications of autoimmune disease.
Neuropsychiatric systemic lupus erythematosus (NPSLE), also called neurolupus, refers to systemic lupus erythematosus (SLE) with peripheral or central nervous system (CNS) involvement and cognitive and/or psychiatric effects. The incidence of NPSLE is not established, but some experts suggest that approximately 50% of patients with SLE develop psychiatric or neurologic symptoms at some point. NPSLE can manifest in a variety of ways, depending on whether the CNS or peripheral nervous system is affected. Some CNS-related manifestations include aseptic meningitis, cerebrovascular disease, demyelinating syndrome, or a movement, mood, or seizure disorder, among other presentations. Peripheral nervous system involvement can manifest with acute inflammatory demyelinating polyradiculopathy (Guillain-Barré syndrome), an autonomic disorder, myasthenia gravis, or cranial neuropathy, among other presentations. A workup for neuropsychiatric SLE involves cerebrospinal fluid investigations and imaging studies, in addition to the serologic and nonspecific laboratory tests used in all cases of suspected SLE.
Indications for Testing
Testing for SLE is appropriate in patients with disease manifestations in two or more organ systems (see Quick Answers above and Classification Criteria below).
Classification Criteria
The American College of Rheumatology (ACR) and the European League Against Rheumatism (EULAR) released updated, joint classification criteria for SLE in 2019 to replace the 1997 ACR criteria for SLE. The updated criteria are intended to reflect the increased understanding of SLE as a disease and improve on the sensitivity and specificity of the previous criteria. The Systemic Lupus International Collaborating Clinics (SLICC) has also developed widely used classification criteria. , Both the ACR-EULAR and the SLICC criteria include a combination of laboratory and clinical findings.
The criteria listed in the table below are considered applicable to SLE only when the clinical findings are not better explained by another condition.
Initial Criterion | |
---|---|
ANAa | ANA titer of ≥1:80 on HEp-2 cells or an equivalent positive ANA test (ever) |
Additional Immunologic Criteriab
| Clinical Finding (Score) (Only highest score in each domainc is counted) |
SLE-specific antibodies | Anti-dsDNA antibodies OR Anti-Smith antibodies (6) |
Complement proteins | Decreased C3 OR decreased C4 (3) Decreased C3 AND decreased C4 (4) |
Antiphospholipid antibodies | Anticardiolipin antibodies OR Anti-β2GP1 antibodies OR Lupus anticoagulant (2) |
Additional Clinical Criteriab | Clinical Finding (Score) (Only highest score in each domainc is counted) |
Constitutional | Fever (2) |
Hematologic | Leukopenia (3) Thrombocytopenia (4) Autoimmune hemolysis (4) |
Neuropsychiatric | Delirium (2) Psychosis (3) Seizure (5) |
Mucocutaneous | Nonscarring alopecia (2) Oral ulcers (2) Subacute cutaneous OR discoid lupus (4) Acute cutaneous lupus (6) |
Serosal | Pleural or pericardial effusion (5) Acute pericarditis (6) |
Musculoskeletal | Joint involvement (6) |
Renal | Proteinuria >0.5 g/24 hrs (4) Renal biopsy class II or V lupus nephritis (8) Renal biopsy class III or IV lupus nephritis (10) |
aPatients must have a positive ANA result (at any point in time) to be classified as having SLE, according to the 2019 ACR/EULAR criteria. bA single occurrence of a listed condition is adequate to meet criteria; conditions do not need to occur simultaneously. cThe term “domains” refers to the various categories, such as complement proteins, or constitutional, hematologic, or neuropsychiatric findings, etc. Anti-β2GP1, anti-beta-2 glycoprotein 1; anti-dsDNA, anti-double-stranded DNA; C3, complement 3; C4, complement 4 |
Laboratory Testing
Diagnosis
An initial evaluation for SLE involves both nonspecific and serologic testing.
Nonspecific Testing
Nonspecific laboratory tests can be helpful to identify organ involvement and assess inflammation in patients with suspected SLE. Such tests include CBC, urinalysis, a comprehensive metabolic panel, and a direct Coombs test. Erythrocyte sedimentation rate (ESR) and/or C-reactive protein (CRP) tests are also useful: ESR levels correlate with disease activity, whereas CRP levels will often be low or normal unless infection is present.
Serologic Testing
Serologic testing is a critical component of the assessment for SLE. A diagnosis of SLE should not be made unless at least one autoantibody or complement deficiency is determined to be present.
Antinuclear Antibodies
ANA testing is a recommended initial screening test for SLE. However, ANAs are not specific for SLE and are seen in a variety of other connective tissue diseases, some infections, and malignancies, and are detected in elderly patients and even in some healthy individuals. In patients with positive ANA results, SLE is unlikely unless there are accompanying features that suggest an autoimmune rheumatic disease. , , Further serologic testing is indicated if titers are 1:40 or higher. The 2019 ACR/EULAR updated classification criteria requires a positive ANA result at least once, although a small number of patients with SLE are ANA negative.
ANA results are reported with endpoint titers and patterns. For comprehensive information on patterns and their clinical associations, refer to the International Consensus on ANA Patterns website.
Visit the ARUP Consult Connective Tissue Disease topic for additional information about ANA testing, including a comparison of ANA testing methods, in systemic autoimmune rheumatic diseases.
Other Autoantibodies
Following a positive ANA test in patients with suspected SLE, additional serologic testing is recommended and may include tests for the autoantibodies listed below. Tests for combinations of autoantibodies are also available in panels (see ARUP Lab Tests).
Autoantibodies | Comments |
---|---|
Anti-dsDNA and anti-Smith antibodies | In patients with clinical findings consistent with SLE, positivity is highly predictive of SLE diagnosis |
Antiphospholipid antibodies: OR Antibodies directed against a mixture of phosphatidylserine, phosphatidic acid, and β2GP1 antigens | Elevated levels of any of these markers increase likelihood of SLE Presence is associated with a greater risk of arterial/venous thrombotic events and pregnancy complications in SLE Diagnosis of APS should trigger evaluation for SLE because APS can overlap with or evolve into SLE |
Anti-SSA-52, SSA-60 (Ro), anti-SSB (La) | More likely to be found in Sjögren syndrome but also associated with SLE with photosensitivity and with subacute cutaneous SLE |
Anti-RNP antibodies | Presence may indicate an overlap condition like MCTD |
C1q antibodies | Associated with renal involvement in SLE; helps to identify patients with increased risk for renal impairment and can be useful to guide monitoring in these patients |
Antihistone antibodies | Reportedly detected in all cases of drug-induced SLE Also associated with a small percentage of rheumatoid arthritis, primary biliary cholangitis, and systemic sclerosis cases |
Anti-P antibodies | Once considered useful to assess patients with possible neuropsychiatric SLE; now believed to have limited diagnostic value |
anti-P, antiribosomal P; anti-RNP, antiribonucleic protein; MCTD, mixed connective tissue disease Sources: Gordon, 2017 ; Lam, 2016 ; Joseph, 2010 ; Karimifar, 2013 |
Complement Components
Increased complement consumption is typical in active SLE, and complement testing is routinely performed as part of the serologic workup. Tests for total complement as well as C3 and C4 are useful to support an SLE diagnosis and for disease monitoring (see Monitoring). Because C3 and C4 levels correlate with disease activity, results can help to rule out active disease, particularly renal disease. Decreased C3 and C4 levels may be associated with glomerulonephritis in SLE.
Circulating Immune Complexes
Immune complexes (antigen-antibody complexes) that form in tissue or circulate in the bloodstream are involved in SLE pathogenesis. Circulating immune complexes can deposit in tissues and induce inflammatory processes, and those that bind to C1q have known associations with SLE, particularly SLE with lupus nephritis. Tests to detect these immune complexes are considered useful to assess disease activity in patients with SLE.
Cerebrospinal Fluid Analysis
Cerebrospinal fluid (CSF) investigations are indicated to assess patients for suspected neuropsychiatric systemic lupus erythematosus (NPSLE), also called neurolupus. Recommended CSF analysis includes cell count, glucose, protein, culture, and oligoclonal band assessment.
Other Testing
Imaging studies are useful in patients with suspected NPSLE, and may include magnetic resonance imaging (MRI) or computed tomography (CT) scanning of the brain and/or spine, as well as magnetic resonance angiography if vascular involvement is suspected. Other testing is indicated for patients with manifestations of specific organ involvement; eg, patients with suspected renal involvement may need assessment with renal biopsy.
Monitoring
The American Academy of Family Physicians (AAFP) recommends that patients with SLE be monitored with the following tests every 3-6 months: C3 and C4, serum creatinine, anti-dsDNA antibody, CBC, and urinalysis. Other tests that may be useful include a CRP or ESR test; antiphospholipid, anti-SSA (Ro), anti-SSB (La), and anti-RNP antibody, immunoglobulin, and direct Coombs tests; renal, liver, and thyroid function tests; and other tests as clinically indicated. Tests to detect circulating immune complexes (C1q binding and anti-C1q IgG antibody assays) are also considered helpful in monitoring patients with SLE. Additional or more frequent testing is indicated in patients receiving specific treatments and in those who develop particular complications of SLE, such as hemolytic anemia or lupus nephritis.
The British Society of Rheumatology (BSR) recommends monitoring as often as every 1-3 months for active disease and after a disease flare, and monitoring every 6-12 months in patients with low or no disease activity, or stable disease after treatment. In addition, because antiphospholipid antibodies are linked to pregnancy complications and thrombotic events, the BSR recommends that patients with SLE who previously tested negative for antiphospholipid antibodies be retested before pregnancy or surgery or if a vascular event has occurred. The BSR also recommends testing for anti-SSA (Ro) and anti-SSB (La) antibodies before pregnancy because of the association between these antibodies and neonatal lupus.
SLE is linked to an increased risk for cardiovascular disease, including myocardial infarction and rapidly progressive atherosclerosis. Patients with an established diagnosis of SLE should be periodically assessed for cardiovascular disease, hypertension, dyslipidemia, and diabetes mellitus. Other complications of SLE include circulatory disease, infections, renal disease, non-Hodgkin lymphoma, lung cancer, and osteoporosis, and monitoring for these conditions is recommended. Yearly evaluation for organ damage is also recommended.
ARUP Laboratory Tests
Semi-Quantitative Indirect Fluorescent Antibody (IFA)
Qualitative Enzyme-Linked Immunosorbent Assay/Semi-Quantitative Indirect Fluorescent Antibody
Qualitative Enzyme-Linked Immunosorbent Assay/Semi-Quantitative Indirect Fluorescent Antibody/Semi-Quantitative Multiplex Bead Assay/Semi-Quantitative Enzyme-Linked Immunosorbent Assay
Quantitative Immunoturbidimetry/Semi-Quantitative Enzyme-Linked Immunosorbent Assay/Semi-Quantitative Indirect Fluorescent Antibody/Quantitative Chemiluminescent Immunoassay/Semi-Quantitative Multiplex Bead Assay
Semi-Quantitative Enzyme-Linked Immunosorbent Assay/Semi-Quantitative Indirect Fluorescent Antibody
Semi-Quantitative Multiplex Bead Assay
Semi-Quantitative Enzyme-Linked Immunosorbent Assay/Semi-Quantitative Multiplex Bead Assay
Semi-Quantitative Enzyme Immunoassay (EIA)
Quantitative Enzyme-Linked Immunosorbent Assay/Quantitative Multiplex Bead Assay
Electromagnetic Mechanical Clot Detection/Chromogenic Assay/Semi-Quantitative Enzyme-Linked Immunosorbent Assay (ELISA)
Semi-Quantitative Enzyme-Linked Immunosorbent Assay
Semi-Quantitative Enzyme-Linked Immunosorbent Assay
Electromagnetic Mechanical Clot Detection/Chromogenic Assay
Semi-Quantitative Enzyme-Linked Immunosorbent Assay
Semi-Quantitative Multiplex Bead Assay
Semi-Quantitative Multiplex Bead Assay
Semi-Quantitative Multiplex Bead Assay
Semi-Quantitative Enzyme-Linked Immunosorbent Assay
Semi-Quantitative Enzyme-Linked Immunosorbent Assay
Semi-Quantitative Multiplex Bead Assay
Quantitative Immunoturbidimetry
Quantitative Immunoturbidimetry
Semi-Quantitative Enzyme-Linked Immunosorbent Assay
Semi-Quantitative Enzyme-Linked Immunosorbent Assay
Quantitative Turbidimetry
Quantitative Electrophoresis
Quantitative Enzymatic Assay
Qualitative Isoelectric Focusing/Electrophoresis
Qualitative Isoelectric Focusing/Electrophoresis/Quantitative Immunoturbidimetry
References
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Aringer M, Costenbader K, Daikh D, et al. 2019 European League Against Rheumatism/American College of Rheumatology classification criteria for systemic lupus erythematosus. Ann Rheum Dis. 2019;78(9):1151–1159.
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Fanouriakis A, Kostopoulou M, Alunno A, et al. 2019 update of the EULAR recommendations for the management of systemic lupus erythematosus. Ann Rheum Dis. 2019;78(6):736–745.
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International Consensus on Antinuclear Antibody Patterns. Nuclear patterns. International Consensus on ANA Patterns. [Updated: 2019; Accessed: Mar 2021]
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Karimifar M, Sharifi I, Shafiey K. Anti-ribosomal P antibodies related to depression in early clinical course of systemic lupus erythematosus. J Res Med Sci. 2013;18(10):860-864.
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Wener MH. Tests for circulating immune complexes. Methods Mol Biol. 2014;1134:47-57.
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Positive nuclear patterns reported include homogeneous, speckled, centromere, nucleolar, or nuclear dots; positive cytoplasmic patterns reported include reticular/AMA, discrete/GW body-like, polar/golgi-like, rods and rings, or cytoplasmic speckled patterns