From the Guidelines
CRP is often normal in lupus patients due to the suppressive effect of interferon-alpha on IL-6 production, which is the primary driver of CRP synthesis, as reported in the 2010 European League Against Rheumatism recommendations 1. This occurs because lupus pathogenesis involves the suppression of interleukin-6 (IL-6) in the liver, leading to normal or low CRP levels despite active inflammation. Some key points to consider when evaluating CRP in lupus patients include:
- The significance of C reactive protein (CRP) in SLE remains controversial, with many authors reporting that patients with SLE rarely have elevated CRP levels 1
- In the case of a significant increase in CRP along with clinical suspicion, a superimposed infection should be excluded, especially in the presence of very high values (>50 mg/litre) 1
- Instead of elevated CRP, patients with active lupus typically show increased erythrocyte sedimentation rate (ESR) and complement consumption (low C3 and C4 levels)
- CRP can still rise in lupus patients when they develop infections or specific complications like serositis or synovitis
- When monitoring lupus patients, physicians should rely on ESR, complement levels, anti-dsDNA antibodies, and specific organ function tests rather than CRP to assess disease activity, as suggested by the 2010 European League Against Rheumatism recommendations 1.
From the Research
CRP Levels in Lupus
- CRP levels can be normal in lupus patients, even during active disease, as seen in studies 2, 3.
- In some cases, CRP levels may not accurately reflect disease activity, as other acute-phase proteins may be more reliable indicators of inflammation and organ damage 3.
- The presence of anti-DNA antibodies can be a stronger indicator of disease activity than CRP levels, especially in patients with inactive disease or local infections 2.
Factors Influencing CRP Levels
- Infections and inflammatory processes can cause significant increases in CRP levels, regardless of lupus activity 2, 3.
- Active nephritis is often characterized by lower serum CRP levels, which could have important pathogenic implications 3.
- Arthritis, on the other hand, is associated with higher CRP levels, making it a useful marker for this specific manifestation of lupus 3.
Complex Role of CRP in Lupus
- CRP can play a beneficial role in autoimmune conditions like lupus by contributing to the clearance of cell remnants and immune complexes 4.
- However, CRP can also constitute an autoantigen in lupus, highlighting the complex and multifaceted nature of its role in the disease 4.
- The relationship between CRP, inflammation, and cardiovascular disease is also an important consideration in lupus patients, who are at increased risk of cardiovascular and cerebrovascular diseases 4.