What is the additive in the BCx2 tube?

The correct answer is nutrient broth. The BCx2 tube is specifically designed for blood culture testing, and its additive, nutrient broth, helps to support the growth of microorganisms from a blood sample. This additive creates an optimal environment for detecting any potential pathogens by fostering their growth, which is crucial in diagnosing infections in patients.

The other additives mentioned, such as EDTA, sodium citrate, and heparin, are commonly used in different types of tubes for various laboratory tests, but they are not suitable for blood cultures. EDTA is often used as an anticoagulant for hematology tests, sodium citrate is typically employed for coagulation studies, and heparin is another anticoagulant used for tests that require plasma samples. Each of these additives serves specific functions that are not aligned with the purpose of the BCx2 tube, which is centered on cultivating microorganisms from a blood sample.