Levels between 1 mg/dL and 3 mg/dL are considered a moderate risk, and a level greater than 3 mg/dL is considered high risk for the development of cardiovascular disease. Hs-CRP is usually reported in mg/dL. When used for cardiac risk stratification, hs-CRP levels less than 1 mg/dL are considered low risk. However, in general, the result is reported in either mg/dL or mg/L. Lab values vary, and there is no standard at present. To detect lower levels of CRP (0.3 to 1.0 mg/L), high-sensitivity CRP methods are recommended as the usual CRP detection tests are less precise. High-sensitivity CRP only denotes the assay process used, allowing for detection of lower levels of CRP and not a different, or more specific, differential diagnosis. Immunoassays and laser nephelometry are the methods to quantify CRP levels and are cheap, accurate, and fast. Complications include oozing at the draw site, bruising or mild tenderness at the site, or very rarely, infection at the venipuncture site. Other bodily fluids, such as synovial fluid, can be tested for in this manner but frequently are not. There are no special procedures required. Fasting is not required before the blood draw. The patient's medications should be reviewed, as these can affect the outcome of the test. He or she removes the band from the patient's arm and then removes the needle and applies pressure to the venipuncture site until hemostasis occurs, usually within one minute. Once the area air dries, the practitioner introduces a needle into the vein and draws a vial of blood. The phlebotomist palpates the vein to confirm the location and cleanses the area with an alcohol prep pad. The phlebotomist secures a snug rubber band around the upper arm, and the patient pumps his or her fist several times. A phlebotomist performs the procedure in most cases. More modest elevations tend to be associated with a broader spectrum of etiologies, ranging from sleep disturbances to periodontal disease.Ī blood specimen is taken from a peripheral venous draw. Trauma can also cause elevations in CRP (alarmin response). However, markedly elevated levels of CRP are most often associated with an infectious cause (an example of pathogen-associated molecular pattern recognition). These include acute and chronic conditions, and these can be infectious or non-infectious in etiology. There are numerous causes of an elevated C-reactive protein. Persistently elevated CRP levels can be seen in chronic inflammatory conditions such as chronic infections or inflammatory arthritides such as rheumatoid arthritis.
Īs compared to the erythrocyte sedimentation rate, which is an indirect test for inflammation, the levels of CRP rise and fall rapidly with the onset and removal of the inflammatory stimulus, respectively. It can also worsen tissue damage in certain cases by activation of the complement system and thus inflammatory cytokines. It can activate the classic complement pathway and also activate phagocytic cells via Fc receptors to expedite the removal of cellular debris and damaged or apoptotic cells and foreign pathogens. This can become pathologic, however, when it is activated by autoantibodies displaying the phosphocholine arm in auto-immune processes, such as idiopathic thrombocytopenic purpura (ITP). It plays a role in the recognition and clearance of foreign pathogens and damaged cells by binding to phosphocholine, phospholipids, histone, chromatin, and fibronectin. It has been demonstrated to have some protective properties in animal studies on lung tissue in alveolitis by reducing neutrophil-mediated damage to the alveoli and protein leakage into the lung.ĬRP has both proinflammatory and anti-inflammatory properties. There is some question about whether dysregulation of the role of CRP in the clearance of apoptotic cells and cellular debris plays a role in the pathogenesis of systemic lupus erythematosus (SLE), but this has not been definitively demonstrated. The name CRP arose because it was first identified as a substance in the serum of patients with acute inflammation that reacted with the "c" carbohydrate antigen of the capsule of pneumococcus.ĬRP is a pentameric protein synthesized by the liver, whose level rises in response to inflammation. CRP is an acute-phase reactant protein that is primarily induced by the IL-6 action on the gene responsible for the transcription of CRP during the acute phase of an inflammatory/infectious process. C-reactive protein (CRP) was discovered by Tillett and Francis in 1930.
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