title: Factor X assays using chromogenic substrate S-2222.
abstract: Factor X was assayed using chromogenic substrate S-2222 for four patients with severe factor X deficiency and for nine patients with homozygous or heterozygous factor X Friuli disorder. Factor X Friuli disorder is characterized by the presence of an abnormal factor X that is normally activated by Russell's viper venom, but is not activated by tissue thromboplastins. The levels of factor X found in factor X deficiency varied between 2 and 10% of normal and therefore were higher than those found in the same plasmas using "clotting" methods (1% or less than 1% of normal). The levels of factor X found in homozygous factor X Friuli patients varied between 4 and 11% of normal, and therefore were practically identical to those found by means of clotting methods that employed tissue thromboplastins (7-9% of normal). These values were definitely lower than those obtained using a Russell's viper venom and cephalin mixture as thromboplastin (82-92%). A similar pattern was observed for patients heterozygous for the abnormality. These findings indicate that "amidolytic" methods are not necessarily identical to clotting methods. Furthermore, they indicate that substrate S-2222 is not specific for factor X.
mesh_terms: D001780:Blood Coagulation Tests; D005170:Factor X / Q000032:analysis*; D005171:Factor X Deficiency / Q000097:blood* / Q000151:congenital / Q000175:diagnosis; D006801:Humans; D007020:Hypoprothrombinemias / Q000097:blood*; D009842:Oligopeptides; D011517:Prothrombin Time
chemical_list: D009842:Oligopeptides; C015608:benzoyl-Ile-Glu-Gly-Arg-p-nitroanilide; D005170:Factor X