Which of the following tubes contains an anticoagulant?

The pink tube contains an anticoagulant, specifically EDTA (ethylenediaminetetraacetic acid), which is used in blood collection for various blood tests and transfusion purposes. The anticoagulant properties of EDTA help to prevent blood clotting by binding calcium ions in the blood, thereby preserving the sample for accurate testing.

In contrast, the SST (serum separator tube) is designed to facilitate the separation of serum from blood cells and does not contain an anticoagulant. The red tube typically is plain or may contain a clot activator but is also not an anticoagulant tube. The gray tube contains sodium fluoride or antiglycolytic agent, which does have specific preservative properties but primarily functions to inhibit glycolysis, rather than to act as an anticoagulant in the conventional sense. This distinction is crucial for understanding the various functions and uses of different blood collection tubes.