C-Reactive Protein
المؤلف:
Mary Louise Turgeon
المصدر:
Immunology & Serology in Laboratory Medicine
الجزء والصفحة:
5th E, P94-95
2025-07-07
473
Traditionally, CRP has been used clinically for monitoring infection, autoimmune disorders and, more recently, healing after a myocardial infarction (MI). Levels of CRP parallel the course of the inflammatory response and return to lower undetectable levels as the inflammation subsides. CRP demonstrates a large incremental change, with as much as a 100-fold increase in concentration in acute inflammation, and is the fastest responding and most sensitive indicator of acute inflammation. CRP increases faster than ESR in responding to inflammation, whereas the leukocyte count may remain within normal limits despite infection. An elevated CRP level can signal infection many hours before it can be confirmed by culture results; therefore, treatment can be prompt. Because of these characteristics, CRP is the method of choice for screening for inflammatory and malignant organic diseases and monitoring therapy in inflammatory diseases.
Elevations of the CRP level occur in about 70 disease states, including septicemia and meningitis in neonates, infections in immunosuppressed patients, burns complicated by infection, serious postoperative infections, MI, malignant tumors, and rheumatic disease. Measurement of CRP may add to the diagnostic procedure in select cases (e.g., differentiation between bacterial and a viral infection). An extremely elevated CRP level suggests a possible bacterial infection (see later, procedure description). In general, CRP is advocated as an indicator of bacterial infection in at-risk patients in whom the clinical assessment of infection is difficult to make, but a lack of specificity rules out CRP as a definitive diagnostic tool.
Levels of CRP rise after tissue injury or surgery. In uncomplicated cases, the CRP level peaks about 2 days after surgery and gradually returns to normal levels within 7 to 10 days. If the CRP level is persistently elevated or returns to an increased level, it may indicate underlying sepsis preceding clinical signs and symptoms and should alert the clinician to postoperative complications.
In clinical practice, CRP is particularly useful when serial measurements are performed. The course of the CRP level may be useful for monitoring the effect of treatment and for early detection of postoperative complications or intercurrent infections. In rheumatoid arthritis (RA), the CRP level reflects short-term and long-term disease activity. Monitoring of CRP levels allows for early prediction of response to a particular drug, often months before clinical and radiologic confirmation are possible. In disorders such as RA, CRP can be used to assess the effect of antiinflammatory drugs (e.g., aspirin) and the nature of their action. Aspirin-like drugs do not suppress acute-phase proteins in inflammation, allowing optimal therapy in the shortest time and minimizing ongoing inflammation and joint damage. Assessment of CRP is also valuable in monitoring therapy and disease activity in other arthritides. Rheumatic fever and Crohn’s disease can also be monitored by CRP. In addition, CRP level assessment has been found to enhance the value of traditional enzyme measurements in MI.
In a number of chronic inflammatory diseases, however, CRP is an unreliable indicator. CRP values may be normal when other acute-phase proteins are altered in disorders such as SLE, dermatomyositis, and ulcerative colitis. SLE shows little or no CRP response, despite apparently active inflammation.
Both CRP and low-density lipoprotein (LDL) cholesterol levels are known to be elevated in persons at risk for cardiovascular disease. CRP level may be a stronger predictor of cardio vascular events than LDL cholesterol, an established benchmark of cardiovascular risk.
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