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Table 3: Diagnostic tests in AHA in the elderly (see Huth-Kuhne et al., modified [5]).

(1) Mixing test: prolongation of the aPTT in a mixture of  patient and normal plasma after 1-2 h incubation  compared to an immediate mix is typical of FVIII  autoantibodies. (2) Clotting factor measurement: patients should have FVIII,  IX, X, XI, XII levels measured; an isolated low FVIII level  is suggestive of AHA. (3) Quantification of the inhibitor titer: Bethesda assay, the test  should be repeated to confirm the presence of the inhibitor.