American Medical Certification Association (AMCA) Phlebotomy Practice Exam

The presence of heparin as the additive in a dark green tube is significant in the context of laboratory testing. Heparin is an anticoagulant that functions by inhibiting thrombin and factor Xa, which are critical components in the body's blood clotting cascade. This property makes heparin particularly valuable for tests that require plasma samples, as it prevents the blood from clotting during the collection process.

Dark green tubes are commonly used for a range of tests that necessitate the use of plasma for accurate results, including specific chemistry tests and certain types of blood gases. The use of this additive allows for a variety of laboratory analyses while maintaining the integrity of the blood sample by avoiding clot formation.

In the laboratory setting, it's essential to use the appropriate tube with the correct additive since different additives can alter the way blood components behave and may affect the outcome of various tests. This is why understanding the role of heparin in dark green tubes is crucial for phlebotomists and medical laboratory technicians.