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C-reactive protein (CRP), initially described by Tillet and Francis in 1930, was discovered in serum of patients with pneumonia and not isolated until 1941. The name was derived from the ability of C-reactive protein to react with the C-polysaccharide isolated from pneumococcal cell walls into a complex. C-reactive protein was observed early in the course of infection, and its disappearance with the resolution of the infection suggested its function in the immunological host defense.1 Therefore, CRP was a frequently requested laboratory test for detection of inflammatory diseases in the 1940s and 1950s.
However, the laboratory methods available at that time were only qualitative in nature, and normal levels could not be detected. The lack of quantitative measurements made it difficult to find any correlation between the severity of a clinical disease and positivity of the test. As a result, the enthusiasm for CRP was lost, and the test was almost nonexistent in the 1970s. During this time, the preferred test for detecting inflammation became the erythrocyte sedimentation rate (ESR). In the 1970s and 1980s, significant advances in isolating CRP and characterizing its physical and chemical nature were made. This resulted in highly sensitive and fast quantitative measurements of CRP. Coupled with advances in technology, CRP can be measured in the picogram range. The laser nephelometric assay is probably the most popular because of its ease, speed, and reproducibility. Approximately 70% of the clinical laboratories in the United States use laser nephelometry for CRP determinations. These developments call for a serious reappraisal of CRP as the most sensitive and reliable clinical laboratory test for detecting acute inflammatory reactions or a change in the severity of such a reaction.
CHARACTERISTICS OF C- REACTIVE PROTEIN
The CRP gene is located on chromosome 1 coding for a single polypeptide of 206 amino acids. Five CRP polypeptides, acting as monomers, noncovalently bind to form a disk-like pentamer with a molecular weight of 118,000. Due to its structure and CaH- -f -dependent binding specificities, CRP is classified as a pentraxin.2 On the basis of its increase in plasma concentration during infection and inflammation, CRP is categorized as an acute-phase protein.
Acute-phase proteins constitute a heterogeneous group of proteins of hepatic origin that share the property of increased plasma concentration during...