What is the normal activated partial thromboplastin time (aPTT) range?

What is the normal activated partial thromboplastin time (aPTT) range?

• A. ~40–60 seconds
• B. ~30–40 seconds
• C. ~20–30 seconds
• D. ~50–70 seconds

Answer: (B)

The main idea is that activated partial thromboplastin time (aPTT) measures how long it takes for a clot to form via the intrinsic and common pathways, using standard reagents. A normal aPTT is typically around 30 to 40 seconds in many laboratories, which is why this range is considered the standard reference. Values longer than that can indicate factor deficiencies or the influence of anticoagulants like unfractionated heparin; values shorter than normal are less common and often reflect lab variation or other factors. Since the question asks for the normal range and one option fits the commonly used reference interval, the 30–40 seconds range is the best choice. Always check the specific lab’s reference interval on the report, as it can vary slightly.

The main idea is that activated partial thromboplastin time (aPTT) measures how long it takes for a clot to form via the intrinsic and common pathways, using standard reagents. A normal aPTT is typically around 30 to 40 seconds in many laboratories, which is why this range is considered the standard reference. Values longer than that can indicate factor deficiencies or the influence of anticoagulants like unfractionated heparin; values shorter than normal are less common and often reflect lab variation or other factors. Since the question asks for the normal range and one option fits the commonly used reference interval, the 30–40 seconds range is the best choice. Always check the specific lab’s reference interval on the report, as it can vary slightly.