Is my aPTT result normal?

For evidence-based information about aPTT (Activated Partial Thromboplastin Time) Test, visit this page.

Does the prolongation indicate bleeding risk?

For evidence-based information about aPTT (Activated Partial Thromboplastin Time) Test, visit this page.

Could lupus anticoagulant be a factor?

For evidence-based information about aPTT (Activated Partial Thromboplastin Time) Test, visit this page.

What factors may be affecting my result?

For evidence-based information about aPTT (Activated Partial Thromboplastin Time) Test, visit this page.

How often should I be retested?

For evidence-based information about aPTT (Activated Partial Thromboplastin Time) Test, visit this page.

Home → Tests → aPTT

aPTT (Activated Partial Thromboplastin Time) Test

⚠️ Update approaching🔬 Evidence: ModerateHematology

Diğer adları: APTT test, Partial thromboplastin time, PTT

⚠️

Discuss your test results with your doctor. This page is for informational purposes only and does not provide a diagnosis.

⚡ Key Facts

• Measures clotting time via the intrinsic and common pathways • Normal: approximately 25–40 seconds • Used for heparin monitoring and bleeding disorder investigation • Lupus anticoagulant may cause prolongation without bleeding risk

🧪 What Does This Test Measure?

The aPTT test measures clotting time through the intrinsic and common pathways, used for heparin monitoring and bleeding disorder investigation.

📋 Why Is It Ordered?

Ordered for bleeding disorder investigation, unfractionated heparin monitoring, and preoperative clotting assessment.

🔧 Preparation

Fasting is generally not required. Blood is collected in a citrated tube. Sample handling and timing are important for accuracy.

📊 Reference Ranges

Normal: approximately 25–40 seconds (varies by laboratory) UFH therapeutic range: typically 1.5–2.5× the control value ⚠️ Ranges vary by laboratory and reagent.

⬆️ High Values

Prolonged aPTT may be associated with heparin therapy, factor deficiencies, lupus anticoagulant, or DIC.

⬇️ Low Values

Shortened aPTT is rarely evaluated clinically. It may be seen with acute phase response or elevated factor VIII.

⚙️ What Can Affect Results?

Medications, sample collection technique, reagent type, elevated CRP or hematocrit, and delayed processing may affect aPTT results.

🔬 Evidence Summary

Moderate evidence: 4 guidelines and 3 reviews.

📚 Most Important Studies on This Topic

International Council for Standardization in Haematology (ICSH) recommendations for the performance and interpretation of activated partial thromboplastin time and prothrombin time mixing tests

Guideline· International Journal of Laboratory Hematology · 2024 · PMID: 39009028

Guidance from the Scientific and Standardization Committee for lupus anticoagulant/antiphospholipid antibodies of the ISTH: Update of the guidelines for lupus anticoagulant detection and interpretation

Guideline· Journal of Thrombosis and Haemostasis · 2020 · PMID: 33462974

How to interpret and pursue an abnormal prothrombin time, activated partial thromboplastin time, and bleeding time in adults

Review· Mayo Clinic Proceedings · 2007 · PMID: 17605969

✅ Key Takeaways

💡

What you learned: aPTT evaluates the intrinsic clotting pathway. It is essential for heparin monitoring and bleeding disorder investigation.

⛔

An aPTT result alone cannot diagnose a bleeding or clotting disorder. Clinical context and additional tests are needed.

🔬 Sources Used on This Page

7 sources · Most recent publication: 2024

📋

Guideline

Expert society and guideline recommendations

sources

📖

Review

Comprehensive topic evaluation

sources

Overall assessment: Evidence level for this topic is moderate. This page is supported by 4 guidelines, 3 reviews.

📝 Questions to Ask Your Doctor

Be prepared for your appointment. Add questions to your list.

📋 References

[PMID: 39009028] International Council for Standardization in Haematology (ICSH) recommendations for the performance and interpretation of activated partial thromboplastin time and prothrombin time mixing tests. International Journal of Laboratory Hematology, 2024.

[PMID: 33462974] Guidance from the Scientific and Standardization Committee for lupus anticoagulant/antiphospholipid antibodies of the ISTH: Update of the guidelines for lupus anticoagulant detection and interpretation. Journal of Thrombosis and Haemostasis, 2020.

[PMID: 27272964] Activated Partial Thromboplastin Time Monitoring of Unfractionated Heparin Therapy: Issues and Recommendations. Seminars in Thrombosis and Hemostasis, 2016.

[PMID: 25168937] Clinical use of the activated partial thromboplastin time and prothrombin time for screening: a review of the literature and current guidelines for testing. Clinical Laboratory Medicine, 2014.

[PMID: 22315259] Evidence-based management of anticoagulant therapy: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: ACCP Evidence-Based Clinical Practice Guidelines. Chest, 2012.

[PMID: 17605969] How to interpret and pursue an abnormal prothrombin time, activated partial thromboplastin time, and bleeding time in adults. Mayo Clinic Proceedings, 2007.

[PMID: 11816725] Towards definition, clinical and laboratory criteria, and a scoring system for disseminated intravascular coagulation. Thrombosis and Haemostasis, 2001.

Last reviewed: 4/2/2026

Next review: 4/2/2027

⚖️ Comparisons

PT/INR vs aPTT→

🔗 Related Topics

🧪 PT/INR (protrombin zamanı)🧪 D-dimer 🧪 Fibrinojen 🧪 Hemogram (trombosit sayısı)

⚖️ This page does not replace medical advice. Make treatment decisions with your doctor.
Content is based on scientific studies indexed in PubMed and current clinical guidelines.