Blood Cultures Are Laboratory Tests

Blood cultures are laboratory tests that are used to detect whether bacterial or viral pathogens have entered the human vascular system. They are typically ordered when a person has symptoms of infection and allow medical personnel to understand which type of pathogen is affecting the individual so that appropriate treatment may be ordered. A typical blood culture is able to reveal a number of problems; from the innocent to the very severe. It is a way to scientifically understand the chemical make-up of the individual's blood at the time of testing. The term "culture," refers to the procedure that blood cells are placed in a medium that allows bacteria or other microorganisms to grow under conditions which allow medical personnel to more accurately identify them (Fischbach and Dunning 535-6).

History- While the first recorded blood transfusion took place in 1665, it was not until 1901 that researchers identified different human blood types, and again not until 1939 that the Rh factor and blood type testing began in earnest. In the 1930s and 1940s blood testing was done to screen for syphilis and rubella as a prerequisite to marriage. Certain basic tests (CBC) and some culturing was done after the 1930s, but it was not really until the post-World War II medical advances and really not until the 1960s that blood cultures became significant diagnostic tools (Kenney).

Method - A blood culture is done with a blood draw. First, the exposed skin is wiped with a disinfectant pad, and then often smeared with an antibacterial solution. This skin sterilization is crucial to prevent contamination from the skin and cause a misdiagnosis. The amount of blood that is drawn is dependent upon the age of the individual -- 5mm in babies, 1-2 mm for older children and up to 5mm for adults. This amount of fluid is quickly replenished, along with the blood cells, the body usually compensates within 24-48 hours. The general rule on blood cultures, based on statistical observation, shows that the higher the volume of blood cultured, the higher the yield of potential cultures. This rule remains true even in the contemporary technological era, in which blood cultures are routinely read by machine or computer (Bouza, Dousa, Rodriguez-Creixems, Lechuz and Munoz).

Uses- Blood cultures are often performed to identify specific strains of bacteria or microorganisms in the blood. Sometimes two or more cultures are ordered at different times, depending on symptoms, for a better understanding of any progression (growth) of pathogens. Often, the doctor will order a complete blood count as well (CBC) which determines if the individual has an increased white cell count that indicates a potential infection. Often, too, the results of the blood culture point to the need to order other tests on the blood, a blood chemistry panel, for instance, which evaluates the health of the individual's organs.