Which one of the following tubes is NOT suitable for drawing a blood culture?

Blood cultures are specifically designed to detect the presence of bacteria or fungi in the blood. The appropriate tubes for this purpose are those that promote optimal growth of microorganisms and prevent contamination of the sample. Blood culture tubes typically contain specific nutrients and are either sterile or contain antimicrobial agents that help in identifying pathogens.

While the plain red tube is not suitable for blood cultures, it’s important to highlight that it does not contain any additives that would promote microbial growth, which is essential for culture tests. The red tube is primarily used for serological tests or when serum is required, as it allows blood to clot and then separates serum from cells. This functionality does not align with the needs of blood culture testing, which requires immediate inoculation into specialized culture media to ensure accurate results.

In contrast, tubes designated for blood cultures are engineered to support the growth of bacteria and fungi, ensuring that any potential pathogens are detected. The pink tube is generally used for blood banking and crossmatching, while the green tube, containing heparin, is typically used for tests requiring plasma. Both of these tubes are not suitable for blood cultures for their own distinct reasons linked to their intended use in specific laboratory tests.