The paper presents the comparative use of algorithms to identify the causes of deficiency of coagulation factors in patients with a prolonged APTT, including the definition of the index of circulating anticoagulant (ICA) and the factor-parallelism (FP) method. The results obtained in children with hereditary hemophilia and adults with acquired hemophilia. It is shown that ICA is an effective method for pre-selection of patients with hereditary hemophilia if you suspect an inhibitor to subsequent confirmation test Bethesda. The method the FP has just proved itself in the diagnosis of acquired forms of hemophilia. The use of FP method is most expedient at the stage of screening to identify inhibitors in the laboratory. Method FP loses diagnostic value if the results of the activity factor in all dilutions is close to zero, which is characteristic for individual variants of hereditary hemophilia.