What is an additional tube that can be used to collect a glucose sample?

The correct choice is the gray tube, which is specifically designed for glucose testing due to its formulation and additive properties. This tube contains sodium fluoride, which is an antiglycolytic agent. Its primary function is to inhibit glycolysis, the process by which glucose is broken down by cells. By preventing this process, the gray tube helps ensure that the glucose levels in the blood sample remain stable and accurate during transport and processing.

The other tubes have different purposes and additives that are not ideal for glucose testing. For instance, the SST (Serum Separator Tube) is used for various serum tests and does not contain the necessary additive to prevent glucose metabolism effectively. PST, or Plasma Separator Tubes, are also employed for specific tests that require plasma rather than focusing on preserving glucose levels like the gray tube does. Pink tubes are primarily used for blood banking and compatibility testing and are not used for routine glucose monitoring.