Infectious

Some microbes, including bacteria, fungi, parasites and viruses, cause infections in humans. These are known as infectious agents or pathogens. Traditional testing techniques for detection of such pathogens includes, for example, growing microbes in cultures followed by identification of the microbe, or testing blood samples for antibodies that people develop in response to an infection by a particular microbe.
In the first stages of the diagnosis of infectious diseases, one of the most frequently used tests is the test for detecting the CRP protein. CRP (C-reactive protein) is an acute phase protein whose concentration is seen to increase as a result of the inflammatory process, most notably in response to pneumococcal (bacterial) infectious, histolytic disease and a variety of disease states. Complement C3 and C4 are other markers used in the diagnosis of infectious diseases. C3 and C4 complements are α-glycoproteins. They are an acute phase reactant whose levels are increased during the acute phase. Low level of C4 complement is found in immune complex diseases and in inherited angioedema, while C3 complement levels are normal.