What can C-reactive protein reflect

In 1930, a substance that can form a complex with capsular polysaccharide (C polysaccharide) in pneumococcal cell wall in the presence of Ca2 + was first found in the serum of patients with acute lobar pneumonia, named C-reactive element; Later, some scholars measured that it was a protein and finally named it C-reactive protein (CRP). More than 90 years have passed since the discovery of CRP, and the academic circles have a certain understanding of its mechanism and clinical application value.

CRP can be used as a sensitive biomarker in bacterial infection, trauma, ischemic cardiovascular disease and other inflammatory states, and can roughly distinguish bacterial infection and viral infection, which has attracted extensive clinical attention. In the field of rheumatic diseases, CRP plays a role in rheumatoid arthritis, systemic lupus erythematosus and other diseases.

With the progress of medical science and technology, the new immunoluminescence method effectively improves the sensitivity in the detection process, which can reach 0.005mg/l. In this way, the detection with ultra-high sensitivity is called hypersensitive C-reactive protein. High sensitivity C-reactive protein and common C-reactive protein belong to the same protein, but their sensitivity, range and mode are different in detection.

In rheumatic diseases, CRP is not always the most commonly used biomarker to reflect inflammation. Other biomarkers also work simultaneously, such as erythrocyte sedimentation rate (ESR) to reflect persistent inflammation.

Systemic lupus erythematosus (SLE) is mainly characterized by the production of a large number of antinuclear antibodies (ANA). CRP is only regarded as a low specificity but rapid adaptive immune antibody. CRP levels are usually consistent with disease activity in an inflammatory state. However, SLE is an exception, and CRP level rarely accurately reflects its disease activity.

However, a large number of CRP responses can be observed in SLE patients with some special manifestations, such as serositis and polyarthritis. Similar to common virus infection, when the CRP level of SLE patients is low, they generally show symptoms such as oral ulcer, pleurisy / pericarditis, leucopenia and so on.

The rheumatoid arthritis (RA) classification standard covers the abnormal level of CRP and / or ESR. CRP > 10mg / L is common in untreated patients with new onset RA.

Other types of arthritis also showed abnormal CRP levels. When gout is in attack, the level of CRP will increase significantly, which is easy to be confused with septic arthritis. In psoriatic arthritis (PSA), higher CRP levels are less common, except in patients with lesions involving large joints. Therefore, the classification standard of PSA does not include the item of abnormal protein level in acute phase.

In giant cell arteritis (GCA), unexplained high levels of CRP and ESR, accompanied by specific symptoms such as weight loss and headache, contribute to the final diagnosis. GCA can be manifested with or without proximal myalgia, which is called rheumatic polymyalgia (PMR). In addition to muscle involvement, the 2012 PMR classification criteria also included age ≥ 50 years, abnormal CRP and / or ESR levels. Elevated CRP levels are extremely common in patients with anti neutrophil cytoplasmic antibody (ANCA) - related vasculitis and may also be associated with a high risk of renal involvement.

CRP is one of the most powerful predictors of cardiovascular disease (CVD) in the general population. It has been shown to promote the disease stages of atherosclerosis, such as endothelial dysfunction, atherosclerotic plaque formation, plaque instability and rupture. CRP is an acute phase protein that stimulates the synthesis of stem cells when the human body is infected by inflammation such as microbial invasion or tissue damage. It is a part of human non-specific immunity and plays a complex role in rheumatic diseases.

 

Cindy