In which collection tube would you expect to find an enzyme inhibitor?

The gray tube is specifically designed to contain additives that help preserve certain substances, which includes enzyme inhibitors. When collecting blood for tests where the measurement or activity of enzymes is crucial, such as in glucose testing or lactate measurements, using a tube with an enzyme inhibitor can prevent the activity of those enzymes from continuing in the collected sample. This ensures that the test results accurately reflect the concentrations present at the time of collection rather than reflecting any changes that could occur post-collection.

The yellow, red, and purple tubes do not contain enzyme inhibitors. The yellow tube typically contains a blood culture media or a clot activator, which is not suitable for tests needing enzyme inhibition. The red tube is often used for serum tests and has no additives, allowing the blood to clot naturally. The purple tube, often used for hematology tests, contains an anticoagulant like EDTA but does not serve the purpose of inhibiting enzyme activity. Therefore, the gray tube is the correct choice for preventing enzyme activity in collected samples.