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Principles of diagnosis

Red flags for acquired haemophilia A include:1,2

If acquired haemophilia A is suspected, a specialist should be consulted as soon as possible3

New onset of bruising or bleeding
No history of bleeding disorders
Patients are elderly or postpartum

Diagnosis is supported by abnormal coagulation results2

Coagulation tests in patients with acquired haemophilia A typically show an isolated prolonged activated partial thromboplastin time (aPTT) and normal prothrombin time2

Regardless of bleeding, an isolated prolonged aPTT should always be investigated3

Normal ranges vary by laboratory, but typical values are:

aPTT:
30-40 s4

Prothrombin time:
10-13 s5

Confirmation of acquired haemophilia A requires specialised tests3

Once other causes of prolonged aPTT have been ruled out, an aPTT mixing study can demonstrate that factor VIII inhibitors are present 2,6

Acquired haemophilia A is then confirmed by factor VIII activity <50% 2,6


Diagnosis Chart

Adapted from Knoebl P, et al. 20186

Your role is vital1,3,7

What you can do to support timely diagnosis of acquired haemophilia A:


ONE

Maintain vigilance to spot signs of bleeding8,9

TWO

Take a careful medical history including comorbidity, bleeding history, medication and potential triggers1

THREE

Refer patients with abnormal bleeds to a haematologist as soon as possible1,2,7

SUMMARY

Diagnosing acquired haemophilia A

Consider acquired haemophilia A in patients with new onset of bruising or bleeding and no history of bleeding disorders, particularly if they are elderly or postpartum1,2

Coagulation tests are needed to confirm diagnosis2

If you see abnormal bleeding, alert a haematology specialist1,2,7