CRP (C-reactive protein) is an annular (ring-shaped) pentameric protein found in blood plasma, whose levels rise in response to inflammation. It is an acute-phase protein of hepatic origin that increases following interleukin-6 secretion by macrophages and T cells.C-reactive protein (CRP) is a marker of inflammation in the body. Therefore, its level in the blood increases if there is any inflammation in the body. C-reactive protein, along with other markers of inflammation (erythrocyte sedimentation rate, “sed rate,” or ESR) are also sometimes referred to as acute phase reactants. C-reactive protein is produced by the cells in the liver.C-reactive protein (CRP) is a protein made by the liver and secreted into the blood. It is often the first evidence of inflammation or an infection in the body. Its concentration increases in the blood within a few hours after the start of an infection or another inflammatory injury. The level of CRP can increase many hundred-fold in response to inflammation and then drop relatively quickly as soon as the inflammation passes, making it a valuable test to monitor the effectiveness of treatment.
Here are what the results mean of CRP
- hs-CRP level of lower than 1.0 mg/L — low risk of CVD (heart disease)
- hs-CRP level of 1.0 mg/L and 3.0 mg/L — moderate risk of CVD
- hs-CRP level of more than 3.0 mg/L — high risk of CVD
C-reactive protein
In general, the main causes of increased CRP and other markers of inflammation are a variety of conditions, including
- burns,
- trauma,
- infections, such as pneumonia or tuberculosis,
- heart attack,
- chronic inflammatory diseases such as lupus, vasculitis, or rheumatoid arthritis,
- inflammatory bowel disease, and
- certain cancers.
Ultra Sensitive C-Reactive Protein Blood (HS-CRP)
- C-reactive protein measures an inflammatory response in the body and has been shown to play a role in atherosclerosis and blood clot formation.
- Patients should ask their doctor specifically about HS-CRP, as this test helps determine heart disease risk. Elevated HS-CRP is related to increased risk for heart attack, restenosis of coronary arteries after angioplasty, stroke, and peripheral vascular disease (PVD).
- While elevated cholesterol, LDL and triglycerides and low HDL are all independent risk factors for heart disease and cholesterol build-up, HS-CRP provides additional information about inflammation in the arteries – something not determined by lipid testing alone.
Results
- Less than 1.0 mg/L = Low Risk for CVD
- 1.0 – 2.9 mg/L = Intermediate Risk for CVD
- Greater than 3.0 mg/L High Risk for CVD
Readings of 50 and above are possible, but we generally attribute a level higher than 10 to inflammation due to other conditions, such as an infection, illness, or a serious flare-up of arthritis, can raise CRP levels.
Role in Human Body
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C-reactive protein plays a key role in the host’s defence against infection by activating the complement system and acts as an opsonin for bacterial sequences and nuclear material which has been expressed from a cell during apoptosis, and thus enhances phagocytosis thereby helping to fight infections as well as protect against auto-immune disease.
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It was so named because it reacts with the C-polysaccharide of Streptococcus pneumoniae.
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C-reactive protein elevation is part of the acute-phase response to acute and chronic inflammation.
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The ESR reflects concentrations of fibrinogen and alpha-globulins. It is influenced by immunoglobulins that are not acute-phase proteins. These proteins all have half-lives of days to weeks, and there is a significant lag time between changes at the clinical level and variations in the ESR. This, plus the influence of various other factors on the ESR such as diurnal variation, anaemia, food intake and red cell morphology, makes it an imprecise guide to disease activity in most cases.
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However, ESR remains helpful in certain clinical situations such as the detection of paraproteinaemias, which often do not elicit an acute phase response.
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Raised CRP is 90% sensitive for presence of significant inflammation.
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CRP is predominantly made in the liver and is secreted in increased amounts within six hours of an acute inflammatory stimulus – primarily stimulated by IL-6, but response is enhanced by IL1-B and TNF-a.
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The plasma concentration can double at least every eight hours, reaching a peak after about 50 hours. After effective treatment or removal of the inflammatory stimulus, concentrations can fall almost as rapidly as the 5-7 hour plasma half-life of labelled exogenous C-reactive protein.
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C-reactive protein responses may be reduced by severe hepatocellular impairment, but renal dysfunction can elevate concentrations of C-reactive protein.
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Baseline concentrations for a normal individual is in part genetically determined.
Causes of major elevations of CRP
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Bacterial infections
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Hypersensitivity complications of infections such as erythema nodosum & rheumatic fever
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Some inflammatory diseases such as rheumatoid arthritis, Crohn’s disease, CRP is a good marker of disease activity in Crohn’s (but not for UC) and can be predictive of the need for colectomy.
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Renal transplantation
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Cancers such as lymphoma & sarcoma (usually no higher than 130 and there is a significant correlation with B symptoms), CRP can be a useful prognostic marker for non-Hodgkin lymphoma, multiple myeloma
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Necrosis such as AMI, tumor embolization & acute pancreatitis
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Trauma such as burns and fractures
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Acute viral hepatitis almost all have CRP > 32, and most have CRP > 100
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Mycoplasma pneumonia hepatitis in patients with Mycoplasma pneumoniae infection, mean CRP without hepatitis is around 70, mean CRP with hepatitis is around 140
Causes of minor elevations of CRP
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Inflammatory disease such as systemic lupus erythematosus (SLE), ulcerative colitis, dermatomyositis, Sjögren’s syndrome
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Graft vs host disease
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Alcoholic hepatitis
Causes of minimal elevations of CRP
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Renal impairment
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Low grade inflammation states” such as periodontitis
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Hetabolic syndrome” – the constellation of risk factors for cardiovascular disease and type 2 diabetes, which are generally associated with obesity and insulin resistance.
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7% of “normal” young adults have a CRP > 10mg/L (higher rates for women, blacks, and those aged over 70yrs)approximate upper limit of the reference range (mg/L) for CRP adjusted for age:
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for men: (age in years)/5
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for women: (age in years/5) + 6
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References
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