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Acquired haemophilia A: errors in the diagnosis
M A Kazmi1, W Pickering, M P Smith
1Reference Centre for Haemostatic and Thrombotic Disorders, St. Thomas' Hospital, London, UK.
Summary
Distinguishing specific factor inactivators from non-specific inhibitors is crucial for patients with bleeding disorders. This study clarifies diagnostic challenges, differentiating true factor deficiencies from antiphospholipid antibody interference in coagulation tests.
Area of Science:
- Hematology
- Clinical Coagulation
- Diagnostic Immunology
Background:
- Accurate differentiation between specific factor inactivators and non-specific inhibitors is critical for diagnosing bleeding disorders.
- Prolonged activated partial thromboplastin time (aPTT) with abnormal coagulation tests necessitates careful investigation.
Observation:
- Two patients presented with bleeding and prolonged aPTT, initially suggesting combined factor VIII and IX deficiency due to inactivators.
- Advanced diagnostic techniques, including dilution studies, chromogenic assays, and ELISA, were employed.
Findings:
- Case 1 exhibited a specific factor VIII inactivator, leading to severely reduced factor VIII levels (<1 IU/dl) without factor IX deficiency.
- Case 2 demonstrated a potent antiphospholipid antibody interfering with phospholipid-dependent assays, mimicking factor deficiency.
Implications:
- Antiphospholipid antibodies can significantly confound in-vitro coagulation assays, necessitating cautious interpretation.
- Correctly identifying the cause of abnormal coagulation tests is vital to avoid misdiagnosis and ensure appropriate patient management.