Which laboratory test requires blood collection in a heparin tube?

• A. Hematology test
• B. Coagulation test
• C. Coagulation or hematology test
• D. Blood typing

Answer: (C)

Using a heparin tube provides anticoagulated blood so tests can analyze plasma or unfixed whole blood without clotting. Heparin prevents clot formation by inhibiting thrombin and factor Xa, which is why it’s chosen for tests that rely on liquid blood rather than a clotted sample. In many labs, routine hematology tests use a different anticoagulant (like EDTA) and routine coagulation tests use citrate, but certain hematology procedures and some specialized coagulation studies are performed on heparinized specimens. That overlap is why the option indicating either hematology or coagulation tests is the best answer: both categories include tests that may legitimately use a heparin tube depending on the specific assay.