Key blood tests in lupus
| Test | Finding in lupus | Significance |
|---|---|---|
| ANA | Positive in ~95% | Screening test — sensitive but not specific |
| Anti-dsDNA | Positive in ~70% | Specific for lupus — rises with flares |
| Anti-Sm | Positive in ~25% | Highly specific for lupus |
| Complement C3 & C4 | Low during flares | Consumed by immune complexes |
| CBC | Low WBC, platelets, or Hb | Cytopenias are part of lupus criteria |
| Urine protein | Proteinuria | Lupus nephritis — kidney involvement |
| CRP | Often normal or mildly raised | ESR rises more than CRP in lupus flares |
Symptoms of lupus
The butterfly rash and beyond
Lupus symptoms vary enormously between people and can flare and remit. Common features include: butterfly-shaped facial rash (malar rash) across the cheeks and nose; sun sensitivity (photosensitivity); joint pain and swelling; extreme fatigue; hair loss; mouth ulcers; serositis (pleurisy, pericarditis); kidney disease (lupus nephritis); and neurological symptoms. The ACR/EULAR classification criteria use a combination of clinical features and blood tests to confirm diagnosis.
Lupus and the kidneys (lupus nephritis)
Up to 50% of people with lupus develop lupus nephritis — kidney inflammation from immune complex deposition. It can progress to kidney failure if untreated. Annual urine screening for protein and blood is essential in all lupus patients. A kidney biopsy classifies the severity and guides treatment (hydroxychloroquine, steroids, mycophenolate, belimumab).
Questions to ask your rheumatologist
- Is my anti-dsDNA rising — am I heading into a flare?
- Do I have kidney involvement (lupus nephritis)?
- Should I be on hydroxychloroquine (Plaquenil)?
- How should I protect myself from the sun?