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Antithrombin Activity

Item Value
Approval req'd? No
Available Stat? No
Test code AT
Test group Antithrombin
Performed by Parnassus & Mission Bay Hematology
In House Availability Mission Bay: Test run Monday to Friday 0730 – 1600
If urgently needed, contact MB hematology lab at 476 - 0194

Parnassus: Test run every Monday 0800 – 1600.
If urgently needed, contact Parnassus hematology lab at 353 – 1747

Inform appropriate lab by phone when initiating ECLS anticoagulation protocol
Method Chromogenic substrate
Collection Instructions 1. Check the expiration date on the label of the blue top vacutainer before drawing the patient.

2. For blood collection in a sodium citrate blue top, the tube must be filled to above the Minimum Fill Indicator on the tube. It is crucial to wait and allow the tube to stop filling before removing it from the needle.

3. With use of a butterfly needle, draw about 1 cc using a separate blue top to remove air from tubing, discard the first tube and then draw a second blue top tube filled to the full extent of the vacuum.

4. Tubes should not be filled past the Maximum Fill dashed line by either using a syringe or removing the tube cap.

For patients with Hct's ≥ 55% please contact Hematology (Parnassus: 353-1747, Mission Bay 476-0194) to obtain blue top tubes with adjusted citrate volumes in order to maintain the proper citrate to plasma ratio for coagulation studies.
Container type Blue top filled to full extent of vacuum
Amount to Collect 2.7 mL blood
Sample type Citrated plasma
Preferred volume 1 mL plasma
Min. Volume 0.5 mL plasma
UCSF Rejection Criteria Samples collected in outdated blue top vacutainer. Over-filled or under-filled tubes may be rejected
Processing notes Deliver sample to Hematology asap for processing. Test specimens within four hours of collection or freeze plasma in a plastic tubes at -20C.
Units % activity
Normal range
Adults 79-120%

Neonatal normal ranges based on antithrombin activity are not available. We have included normal ranges below for neonates based on antigen levels which should roughly correlate with activity.

Full term Neonates
Day 1 39-87%
Day 5 41-93%
Day 30 48-108%
Day 90 73-121%

Reference: Andrew M. Et al. Development of the Human Coagulation System in the Full Term Infant. Blood July 1987, 70(1):165-172

Healthy Premature Neonates
Day 1 14-62%
Day 5 30-82%
Day 30 37-81%
Day 90 45-121%
Day 180 52-128%

Reference: Andrew M, et al. Development of the Human Coagulation System in the Healthy Premature Infant. Blood November 1988, 72(5): 1651-1657.
Synonyms ATIII; AT3; AT III; AT Activity; Anithrombin III Activity
Turn around times 1-2 weeks.
Additional information A low level of antithrombin may be associated with an inherited deficiency or with secondary causes such as acute venous thrombosis, liver disease, disseminated intravascular coagulation, heparin therapy, pregnancy, estrogen therapy, and nephropathy with proteinuria

If unusual findings are noted a pathologist review and interpretation may be performed and separately billed for
CPT coding 85300
LOINC code 27811-9
Last Updated 4/13/2017 3:02:19 PM
Entry Number 65
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