Doctor's Assessment Included
Every result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.
Antithrombin III (Concentration)
Antithrombin III Concentration, paired with activity testing, provides complete anticoagulant assessment for older adults managing thrombotic risk.
What It Measures
This test measures the total amount of antithrombin protein (antigen) in your blood, regardless of whether it is functionally active. Results are expressed as a concentration or percentage of normal.
Why It Matters
Combining concentration with activity results classifies antithrombin deficiency type, which influences clinical management and family screening recommendations.
When to Test
This test is typically ordered alongside antithrombin activity to complete the assessment. Timing considerations are the same as for the activity test.
Symptoms
Low Levels
Low antithrombin concentration (Type I deficiency) carries similar thrombotic risk as low activity. Symptoms relate to potential thrombotic events rather than the protein level itself.
High Levels
Elevated antithrombin concentration is generally not clinically significant and does not typically require medical intervention.
Lifestyle Tips
The same recommendations as for antithrombin activity apply: maintain a healthy weight, stay active, avoid smoking, and discuss anticoagulation plans with your healthcare provider for high-risk situations.
Frequently Asked Questions
Why test both activity and concentration?
Activity tells you how well antithrombin works; concentration tells you how much is present. Together they classify deficiency type: Type I (low amount and activity) vs Type II (normal amount but reduced function).
What causes acquired antithrombin deficiency?
Liver disease (reduced production), nephrotic syndrome (urinary loss), DIC (consumption), and heparin therapy (consumption) can all reduce antithrombin levels.
Is antithrombin deficiency common?
Inherited antithrombin deficiency affects about 1 in 2,000-5,000 people. It is less common than Factor V Leiden but carries a higher thrombotic risk per individual.