Final answer:
The light blue top tube used for blood collection contains the anticoagulant sodium citrate, which prevents blood clotting by binding to calcium and is essential for coagulation testing.
Step-by-step explanation:
The light blue top tube commonly used in phlebotomy for blood specimen collection contains an anticoagulant called sodium citrate. This anticoagulant works by binding to calcium in the blood, thereby interrupting the clotting cascade and preventing clot formation. Sodium citrate is typically utilized in tubes intended for coagulation testing because it preserves the coagulation factors in a state that is as close to natural as possible without allowing the blood to clot. It is essential to fill the tube to the designated fill line to maintain the correct ratio of blood to anticoagulant for accurate test results.