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Coagulation

aPTT Test

aPTT (Activated Partial Thromboplastin Time) measures how long it takes blood to form a clot through the intrinsic and common coagulation pathways. It is one of the most commonly ordered coagulation tests and is used to screen for clotting factor deficiencies, monitor heparin therapy, and evaluate bleeding disorders.

Doctor's Assessment Included

aPTT: what this test measures

This test measures the time in seconds for plasma to clot after activation of the intrinsic pathway. A prolonged aPTT may indicate clotting factor deficiencies, the presence of inhibitors such as lupus anticoagulant, or heparin effect.

aPTT: why this value matters

aPTT helps identify bleeding disorders, monitor anticoagulant therapy, and detect clotting inhibitors. It evaluates factors XII, XI, IX, VIII, X, V, II (prothrombin), and fibrinogen.

aPTT: how the blood test works

Referral
No GP referral needed. After the order we arrange the referral through ZorgDomein, within one business day; orders after 17:00 or at the weekend start on the next business day. ZorgDomein emails a barcode, and that barcode is what the draw site needs.
The draw
A blood draw from a vein in the arm, at a partner laboratory's draw site. No home kit, no finger prick.
Which test
on its own €21,-
Where
650+ draw sites run by independent laboratories across the Netherlands. Draw sites

aPTT: when is testing worthwhile?

aPTT is commonly ordered before surgery, when a bleeding disorder is suspected, to monitor heparin therapy, or as part of a coagulation assessment. It is frequently ordered alongside PT/INR.

aPTT: symptoms of a high or low value

Low Levels

A shortened aPTT may suggest a hypercoagulable state and could be associated with increased thrombosis risk. However, a short aPTT alone is rarely clinically actionable.

High Levels

A prolonged aPTT may indicate clotting factor deficiency, vitamin K deficiency, liver disease, lupus anticoagulant, or anticoagulant medication effect. Symptoms of underlying conditions may include easy bruising, prolonged bleeding, or nosebleeds.

aPTT: lifestyle and this value

If aPTT abnormalities are detected, your healthcare provider will investigate the cause. Ensure adequate vitamin K intake through leafy green vegetables. Report any unusual bleeding or bruising to your healthcare provider promptly.

aPTT: frequently asked questions

What is the difference between aPTT and PT?

aPTT evaluates the intrinsic pathway, while PT evaluates the extrinsic pathway. Together they provide a comprehensive view of the coagulation system.

Why might aPTT be prolonged in someone without bleeding?

Lupus anticoagulant can prolong aPTT but paradoxically increases thrombosis risk rather than bleeding risk. This is an important diagnostic distinction.

Does diet affect aPTT?

Diet alone rarely affects aPTT significantly. However, severe vitamin K deficiency or malnutrition can prolong clotting times.

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Medical standards

Dr. Naimi oversees the medical standards behind our content and assessments.

Medical policy
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aPTT

€21,-