From the Guidelines
Yes, there are several blood tests that can help detect a lupus flare, including anti-dsDNA antibodies, complement levels, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP), as recommended by the European League Against Rheumatism 1. The most common markers used to monitor lupus activity include:
- Anti-dsDNA antibodies, which often rise during active disease
- Complement levels (C3 and C4), which typically decrease during flares
- Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), both of which increase with inflammation
- Complete blood count (CBC) to show decreases in white blood cells, red blood cells, or platelets during flares
- Urinalysis to reveal protein or blood in urine if kidneys are affected These tests are usually ordered together as part of regular monitoring for lupus patients. According to the European League Against Rheumatism recommendations for monitoring patients with systemic lupus erythematosus in clinical practice and in observational studies 1, laboratory assessment, including changes in anti-double-stranded (ds) DNA antibody titres, complement levels, and other markers, can be useful in monitoring disease activity. However, laboratory markers don't always correlate perfectly with symptoms, so doctors consider both lab results and clinical symptoms when determining if a flare is occurring. Regular monitoring every 3-6 months is recommended for stable patients, with more frequent testing during suspected flares, as suggested by the EULAR recommendations for the management of systemic lupus erythematosus 1. It's also important to note that the assessment of patients with SLE must include the evaluation of disease activity by a validated index at each visit, organ damage annually, general quality of life, comorbidities, and drug toxicity, as recommended by the European League Against Rheumatism 1.
From the Research
Testing Markers for Lupus Flare
To determine if a lupus flare is occurring, several markers can be tested, including:
- Erythrocyte sedimentation rate (ESR)
- C-reactive protein (CRP)
- The ratio of ESR to CRP
ESR and CRP Levels
Studies have shown that:
- ESR levels can be elevated in both lupus flares and infections, making it difficult to distinguish between the two conditions 2, 3, 4
- CRP levels tend to be lower in lupus flares compared to infections, but can still be elevated in some cases 2, 3, 4, 5
- A high-sensitivity CRP (hsCRP) test can help distinguish between infection and lupus flare, with a cut-off value of above 5-6 mg/dl indicating infection 4
Ratio of ESR to CRP
Research has found that:
- The ratio of ESR to CRP can be useful in distinguishing between lupus flare and infection, with a higher ratio indicating a lupus flare 2
- Each unit increase in the ratio of ESR:CRP was associated with a 17% increase in the odds of fever being attributable to SLE flare compared to infection 2
Clinical Application
In clinical practice, measuring ESR, CRP, and the ratio of ESR to CRP can help healthcare providers:
- Monitor disease activity and distinguish between lupus flare and infection
- Adjust treatment plans accordingly
- Improve patient outcomes by reducing disease exacerbations and organ damage 6