The Assay of Human Factor VII by Means of Modified Factor VII Deficient Dog Plasma

S ummary . An inbred group of beagle dogs deficient in factor VII has been used to provide a reagent for the assay of factor VII in human plasma. Dilutions of human plasma were tested in a one‐stage system with beagle dog plasma, brain extract and calcium chloride. It was found that, if the concentration of factor V in the beagle dog plasma was reduced and a dilute human brain extract used, log clotting time was directly related to log concentration of factor VII. Assays using beagle dog plasma and human plasma deficient in factor VII gave comparable values. A range of factor‐VII activity is reported for normal human plasma samples.