Laboratory Tests for Lupus Workup
For a comprehensive lupus workup, baseline testing should include ANA, anti-dsDNA, anti-Ro, anti-La, anti-RNP, anti-Sm, anti-phospholipid antibodies, C3, and C4 complement levels. 1
Initial Autoantibody Panel
The European League Against Rheumatism (EULAR) recommends the following autoantibody and complement tests at baseline for all patients being evaluated for lupus:
- Antinuclear antibody (ANA)
- Anti-double-stranded DNA (anti-dsDNA)
- Anti-Ro (SSA)
- Anti-La (SSB)
- Anti-ribonucleoprotein (anti-RNP)
- Anti-Smith (anti-Sm)
- Anti-phospholipid antibodies (including anticardiolipin, anti-β2 glycoprotein I, and lupus anticoagulant)
- Complement C3 and C4 levels
Standard Laboratory Tests
In addition to the autoantibody panel, these tests should be performed:
- Complete blood count (CBC)
- Erythrocyte sedimentation rate (ESR)
- C-reactive protein (CRP)
- Serum albumin
- Serum creatinine (or eGFR)
- Urinalysis and urine protein/creatinine ratio 1
Specific Testing Based on Clinical Presentation
For Renal Involvement
- Urine protein/creatinine ratio or 24-hour urine protein
- Urine microscopy
- Renal ultrasound
- Consider renal biopsy if abnormal urinalysis or elevated creatinine persists 1
For Neuropsychiatric Manifestations
- Consider cerebrospinal fluid analysis
- Electroencephalogram if seizures are suspected
- Brain MRI in selected patients with neurological symptoms 2
Follow-up Testing
Re-evaluation of anti-phospholipid antibodies is recommended prior to:
- Pregnancy
- Surgery
- Transplantation
- Use of estrogen-containing treatments
- In the presence of new neurological or vascular events
Anti-Ro and anti-La antibodies should be retested before pregnancy
Anti-dsDNA, C3, and C4 should be monitored to assess disease activity/remission 1
Monitoring Frequency
- During active disease: Monitor every 1-3 months
- For stable disease: Monitor every 6-12 months
- For established nephritis: Monitor protein/creatinine ratio, C3, C4, anti-dsDNA, urinalysis, and blood pressure every 3 months for the first 2-3 years 1, 2
Clinical Pearls and Pitfalls
ANA testing should only be obtained in patients with unexplained involvement of two or more organ systems due to its low predictive value in general populations 3
An ANA titer of 1:40 with characteristic multiorgan involvement may be sufficient for diagnosis, but additional testing (anti-dsDNA, anti-Sm) is recommended for patients who don't meet full clinical criteria 3
Anti-C1q antibodies, alone or in combination with anti-dsDNA, are particularly useful in differentiating proliferative from non-proliferative lupus nephritis 4
Routine laboratory testing beyond the initial autoantibody profile significantly improves diagnostic accuracy in patients with suspected lupus 5
For patients on hydroxychloroquine, baseline and periodic ophthalmologic examinations are essential to screen for retinal toxicity 2
By following this comprehensive laboratory approach, clinicians can accurately diagnose SLE, assess disease activity, monitor organ involvement, and guide treatment decisions to improve patient outcomes.