From the Guidelines
A lupus screen blood test should include anti-dsDNA antibody testing in all ANA-positive cases with clinical suspicion of SLE, using a double-screening strategy with a last-generation SPA as the initial test and CLIFT as the confirmation test. This approach is recommended due to the high inter-method variability in anti-dsDNA antibody testing 1. The guidelines suggest that when ANA is negative, investigating the presence of anti-dsDNA is not recommended except when there is a high degree of clinical suspicion 1.
Some key points to consider when interpreting the results of anti-dsDNA testing include:
- A negative SPA result can be reported directly as negative anti-dsDNA, and the SLE diagnosis would be ruled out, unless other signs of clinical suspicion are present 1
- A positive SPA result followed by a negative CLIFT result does not constitute a solid argument for or against an SLE diagnosis, and further testing, such as anti-nucleosome or antiphospholipid antibodies, may be necessary 1
- The detection of antiphospholipid antibodies can increase the likelihood of SLE, as 30-40% of SLE patients are positive for these antibodies 1
In addition to anti-dsDNA antibody testing, a lupus screen blood test should also include other key components, such as:
- ANA test
- Complete blood count (CBC)
- Complement levels (C3 and C4)
- Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)
- Comprehensive metabolic panel
- Urinalysis
These tests collectively help clinicians establish a diagnosis of lupus and guide treatment decisions. Regular monitoring of these parameters is important for tracking disease activity and treatment response in lupus patients.
From the Research
Lupus Screen Bloods
Lupus screen bloods typically involve testing for antinuclear antibodies (ANA) and other specific autoantibodies to diagnose systemic lupus erythematosus (SLE).
- The ANA test is positive in nearly every case of SLE, but it is not specific for this disease and must be interpreted in the appropriate clinical context 2.
- Key features that warrant ANA testing include unexplained multisystem inflammatory disease, symmetric joint pain with inflammatory features, photosensitive rash, and cytopenias 2.
- The ANA test is the most sensitive test for SLE and is therefore the best screening assay for ruling out its presence 3.
Autoantibody Testing
Autoantibody testing, including anti-native (N)-DNA and anti-Sm (Smith antigen) tests, can be helpful in diagnosing SLE.
- Anti-native (N)-DNA and anti-Sm (Smith antigen) tests are highly specific for SLE and have strong confirmatory powers, even in a patient unlikely to have the disease 3.
- Anti-nucleosome antibodies (anti-nuc) have been established as a disease marker in SLE and their presence is associated with disease activity 4.
- Detection of anti-nuc antibodies could be a better tool for the diagnosis of SLE, and may be useful as an additional disease activity marker to other laboratory tests 4.
Interpretation of Test Results
Interpretation of test results is critical in diagnosing SLE.
- A positive ANA test result can cause diagnostic confusion and unnecessary anxiety for the patient and the physician if not interpreted in the appropriate clinical context 5.
- The presence of anti-DNA antibodies can fluctuate widely, and repeat testing is common, whereas anti-RBP antibodies tend to be stable 6.
- ANA responses can decrease over time due to the natural history of disease or the effects of therapy, and more regular serological testing could illuminate changes relevant to pathogenesis and disease status 6.