Chokri Ben Lamine: Causes and Diagnostic Approach to PTT Prolongation
Chokri Ben Lamine, Adult Hematology and Stem Cell Transplantation Assistant Consultant at Oncology Center of Excellence at King Faisal Specialist Hospital and Research Center, shared a post on, recently shared on X:
“PTT Prolongation — Causes and Approach for Hema Fellows
Causes
- Factor deficiencies: VIII, IX, XI, XII
- Combined defects: Hemophilia A/B, vWD (type 2N), combined factor deficiencies
- Anticoagulants: UFH, argatroban, dabigatran
- Inhibitors: Lupus anticoagulant, acquired FVIII inhibitor
- Consumptive: DIC, massive transfusion
- Contact pathway defects: prekallikrein, HMW kininogen deficiency (no bleeding)
- Liver disease: decreased synthesis of multiple factors
Approach
- Check clinical context — bleeding vs thrombosis
- Repeat PTT — exclude lab error
- Mixing study:
- Corrects → factor deficiency → assay factors VIII, IX, XI, XII
- No correction → inhibitor → lupus anticoagulant or factor inhibitor workup
- If on anticoagulant — check drug level / anti-Xa / TT
- If prolonged with normal PT — think intrinsic pathway
- If prolonged PT and PTT — consider liver disease, DIC, multiple deficiencies
Written Exam Pearl
Isolated prolonged PTT + no bleeding → think lupus anticoagulant or contact factor deficiency.
OSCE Practical Tip
•Scenario: Post-op patient with thrombosis, PTT 65s, normal PT
Don’t rush to transfuse FFP — think lupus anticoagulant → do mixing study + DRVVT.
•Always ask about heparin flushes from lines before labs.
References:
1.Kitchens CS et al. Consultative Hemostasis and Thrombosis, 5th ed, 2023.
2.ISTH Guidelines 2024 — Lupus Anticoagulant Testing.
3.ASH Education Program 2022 — Approach to Abnormal Coagulation Tests.”
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