Lаbоrаtоry results оn а patient with a severe bleeding problem are as follows: Platelet count: 200 x 103/uL prothrombin time: 12.0 sec (control 12.0 sec) APTT: 100 sec (control 32.0 sec) CORRECTION TESTS normal plasma: full correction Based on this data, which of the following will provide the additional information to support the diagnosis you suspect?