Final answer:
Sodium polyanetholesulfanate (SPS) is an anticoagulant by binds calcium ions in blood to prevent clotting and is commonly used in blood culture bottles to reduce immune system activity and allow for the growth of bacteria in the sample.
Step-by-step explanation:
The purpose of an anticoagulant, such as sodium polyanetholesulfanate (SPS), is to prevent blood from clotting. Anticoagulants like SPS are critical in clinical settings when blood samples need to remain fluid for testing or analysis. These substances, typically added to blood collection tubes, impede the blood coagulation process by chelating (binding) calcium ions or inhibiting coagulation factors, which are essential for clot formation.
Compared to other anticoagulants such as heparin, EDTA, or potassium oxalate, SPS acts by binding calcium ions in the blood, similar to EDTA. However, SPS has the unique property of also reducing the actions of complement, which is part of the immune system, hence it is often used in blood culture bottles to prevent the bacteria from being killed by the patient’s immune system before they can be cultured.
For example, when SPS is used in blood culture media, it not only serves as an anticoagulant but also has an additional role in minimizing the effect of certain components of the patient's immune system, such as complement and phagocytes, to encourage the growth of bacteria present in the sample for diagnostic purposes.