Phlebotomy: Blood Collection Additives

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Posted on 18th May 2011 by admin in Uncategorized

There are several different types of additives that can be used in blood collection tubes by a phlebotomy technician.  Each additive has a specific function.  The type of additive that is used depends on the test that has been ordered.  Generally, it is not advised to substitute additives or combine different additives.

Additives come in several different forms. They can be liquid, spray dried, and powdered.  A tube with a powdered additive should be tapped prior to use so that the powder can settle to the bottom of the tube.  Once collection is complete, an additive tube must be inverted 3 to 8 times in order to thoroughly mix the additive with the specimen.

Anticoagulants are substances that do not allow blood to coagulate and form clots.  This is often accomplished by either binding to or precipitating calcium in the blood so that is it unavailable in the coagulation process, or thrombin can be inhibited from forming.  Whole blood specimens should be collected in tubes that contain an anticoagulant additive.  Blood specimens should be gently mixed to prevent hemolysis.

Antiglycolytic agents are substances that are added to prevent glycolysis.  When glycolysis occurs, glucose or blood sugar is metabolized.  An antiglycolytic agent is used to stop the metabolization of glucose.  If glycolysis is not prevented the blood sugar level will decrease at a rate of 10 mg/dL per hour.

Sodium fluoride is the most commonly used antiglycolytic agent.  It is able to preserve the glucose in blood for 3 days and is also effective at inhibiting bacterial growth.  Sodium fluoride tubes have gray stoppers and require eight inversions in order to mix the specimen thoroughly.

Clot activators are used to enhance coagulation and contain substances that provide more surface area for platelet activation.  Silica is a glass and celite is a type of clay that is often used as clot activators.  Silica particles cause the blood to clot within 15 to 30 minutes.  Tubes that contain clot activators should be inverted five times for complete clotting to occur.

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