Which tubes contain heparin as an anticoagulant?

The green top tubes are designated for use with heparin as an anticoagulant. Heparin works by inhibiting thrombin and factor Xa, effectively preventing the clotting of blood. This makes these tubes particularly useful for tests that require plasma samples, such as certain chemistry tests, where the presence of an anticoagulant is necessary to avoid clot formation during the sample preparation process.

The other tubes, while also used in laboratory settings, serve different functions and utilize different additives. Red top tubes typically do not contain any anticoagulant, making them suitable for tests requiring serum. Light blue top tubes contain sodium citrate, which is another anticoagulant but is specifically used for coagulation studies. Yellow top tubes often contain additives like acid-citrate-dextrose (ACD) or are used for blood culture collections, depending on the specific type. Thus, green top tubes stand out as the correct choice for those requiring heparin.