Phlebotomy – Order of Draw Practice Test

Blood cultures are designed to detect the presence of microorganisms, such as bacteria or fungi, in the bloodstream. For this purpose, a whole blood sample is essential. Whole blood retains all the components of the blood, including cells, plasma, and platelets, and is critical for allowing the growth and identification of any pathogens present.

When collecting a blood culture, it is necessary to use whole blood since it provides a living environment for microorganisms to grow. The sample is typically drawn using a sterile technique and often requires both aerobic and anaerobic collection bottles. This method ensures that both types of microorganisms can be effectively cultured and identified.

The other types of samples mentioned, such as serum, plasma, or clotted samples, do not maintain the cellular components necessary for the growth of microorganisms and are therefore not suitable for blood cultures. Serum is obtained after blood has clotted and the cells have been removed, while plasma is derived from whole blood but typically involves anticoagulants that may inhibit microbial growth. Clotted samples also lack the live cells that are crucial for detecting pathogens, making whole blood the appropriate choice.