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Lab Test Dictionary

Antithrombin (III) Chromogenic Assay


Chromogenic Assay


AT III, AT3, Antithrombin III

Specimen Type


Performing Lab


Epic ID


Lab Test Days

Daily; PM Shift

Standard TAT

Batch Testing

Stat TAT

Batch Testing

Collection Information

Specimen Required

1.8-2.7 mL Blood

Container Type

Light Blue (Sodium Citrate)

Collection Instructions

1. The preferred method of specimen collection for coagulation studies is a properly performed VENIPUNCTURE.The specimen may be collected directly into 1.8 or 2.7 mL vacutainer or into a syringe and then transferred immediately into a 1.8 or 2.7 mL vacutainer. 2. The vacutainer tube MUST contain the EXACT amount of blood. It is essential that LT blue top tubes are PROPERLY FILLED. Volume is CRITICAL and the blood (9 parts) to liquid anticoagulant (1 part) must remain intact for correct results. 3. The specimen should be transported to the Laboratory within one hour of collection. 4. SPECIAL INSTRUCTIONS FOR SPECIMENS COLLECTED FROM A LINE: If collecting specimens for coagulation studies from an indwelling line that may contain heparin, it is recommended that the line should be flushed with 5 mL of saline and the first 5 mL of blood or 6-times the line volume (dead space volume of the catheter) be drawn off and discarded before the coagulation tube is filled. For those samples collected from a normal saline lock (capped off venous port) twice the dead space volume of the catheter and extension set should be discarded.

Processing Information - Lab Use Only

Transport Temperature


Specimen Stability

Room Temp: 4 hours following collection

Rejection Criteria

Underfilled or overfilled tubes, clotted, time of collection over 4 hours.

Test Volume Required

1 mL Platelet-Poor Plasma

Minimum Test Volume

0.5 mL Platelet-Poor Plasma

Processing Instructions

Give to Hematology CLS for processing.


In the event of instrument malfunction specimens will be sent to USCD Special Coag for testing. If patient's hematocrit is greater than 55%, contact hematology lab to request a light blue tube with adjusted anticoagulant amount.