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Antithrombin III (Concentration)

Antithrombin III Concentration

Antithrombin III Concentration complements the activity test for comprehensive thrombophilia screening, classifying any deficiency to guide preventive care.

Doctor's Assessment Included

Antithrombin III (Concentration): what this test 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.

Antithrombin III (Concentration): why this value matters

Combining concentration with activity results classifies antithrombin deficiency type, which influences clinical management and family screening recommendations.

Antithrombin III (Concentration): when is testing worthwhile?

This test is typically ordered alongside antithrombin activity to complete the assessment. Timing considerations are the same as for the activity test.

Antithrombin III (Concentration): symptoms of a high or low value

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.

Antithrombin III (Concentration): lifestyle and this value

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.

Antithrombin III (Concentration): 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.