[Control of oral anticoagulation: comparison between Quick and colorimetric factor X determination in 107 patients]

Since monitoring of oral anticoagulation (OA) by prothrombin time (PT) is a source of standardization difficulties, the authors have tested another approach. 107 patients under long term OA were monitored by both PT and a colorimetric factor X assay (in vitro activation of factor X with RVV and assessment of amidolytic activity towards S-2222). The PT values were between 10 and 34% (therapeutic range 15--25%), and factor X levels were between 10 and 44% (therapeutic range 16--24%). The correlation between the two methods was highly significant (r = 0.65, p less than 0.001). In 68% of the patients the two tests gave the same information (55 subjects were adequately, 16 insufficiently and 2 over-anticoagulated). For a slightly broader therapeutic range (PT 15--30%, corresponding to 16--28% factor X) concordant information was obtained in 82% of the patients. During stable OA, PT and factor X assay gave very similar information. An advantage of the latter method is the possibility of automation, while a disadvantage is its insensitivity to factor VII.