What is C-Reactive Protein and what relevance does it have to clinical conditions?
The concentration of a number of plasma proteins increases after tissue injury, whether it is caused by bacterial infection, malignant neoplasia, injury, or surgical procedures. This is known as the acute-phase response and is a non-specific indicator of an inflammatory process. The plasma proteins are collectively termed acute-phase proteins. Their role is to help restore homeostasis. C-reactive protein (CRP) is a member of the acute-phase protein family, and is useful clinically because it is one of the best non-specific biochemical indicators of tissue damage and disease processes.
C-reactive protein is so-called because of its ability to bind to the C protein of pneumococci. When C-reactive protein and other complement proteins bind to bacteria it becomes easier for phagocytic cells such as macrophages to recognise, take in and destroy the bacteria. This defensive process of coating bacteria and other infectious organisms with protein is known as opsonisation.
Careful measurement of CRP levels over a period of time can be very useful in coming to a diagnosis, assessing the effectiveness of treatment, and determining the patient’s prognosis. Levels of C-reactive protein give a better insight into the progress of inflammation than the erythrocyte sedimentation test due to the more rapid kinetics (van Leeuwen and van Rijswijk, 1994). Kits are available now which allow the test for C-reactive protein to be carried out on a blood sample accurately within minutes (Pedrazzi, 1998).
References
Gabay, C., and Kushner, I. (1999) Acute-phase proteins and other systemic responses to inflammation. New England Journal of Medicine, 340(6), 448-454 (Feb 11).
Pedrazzi, A.H. (1998) Acute phase proteins: clinical and laboratory diagnosis. A review. Ann Pharm Fr, 56(3), 108-114.
van Leeuwen, M.A., and van Rijswijk, M.H. (1994) Acute phase proteins in the monitoring of inflammatory disorders. Baillieres Clinical Rheumatology, 8(3), 531-552 (Aug).
