Knowledge Check

What clotting factors may be deficient or inhibited if the aPTT is elevated and the PT is normal?

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Factors in the intrinsic pathway: FXII, FXI, FIX, FVIII

Is an isolated elevation of the aPTT consistent with a diagnosis of lupus anticoagulant?

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Yes

What does the failure of normal plasma to correct an elevated aPTT indicate?

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The presence of an inhibitor

If the mixing study fails to correct the aPTT, what is the next diagnostic step?

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If a patient with thrombosis or without bleeding, a lupus anticoagulant is indicated. If bleeding is present, specific factor assays.

What proportion of patients with acquired hemophilia A are idiopathic?

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About 50%

What is the Bethesda assay used for?

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To determine the titer of the inhibitor

What is the first line treatment for bleeding in a patient with acquired hemophilia A?

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Bypassing agent: either rFVIIa or aPCC (FEIBA)

Besides control of bleeding, what other type of treatment is a priority in these patients

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Immunosuppressive agents to eradicate the inhibitor

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