Summary
Prothrombin has been assayed by means of 7 different techniques in the patients so
far known to have the abnormal factor X (factor X Friuli) coagulation disorder. The
methods were: classical one-stage method, Iowa two-stage method, Oxford two-stage
method, a modified Hjort’s method using Stypven-Cephalin, a modified Jobin and Esnouf’s
method using Tiger venom, the Staphilocoagulase method and an immunological method
with anti-human prothrombin rabbit serum. In all cases a normal prothrombin level
was found. In the two-stage procedures a normal thrombin activity was obtained only
when normal serum was added to the system.
A good correlation was found between the several methods used.
In subjects known to be heterozygote for the abnormal factor X coagulation disorder,
prothrombin level and activity has been found to be normal too. These data suggest
that the abnormal factor X (factor X Friuli) coagulation disorder is due to a distinct
factor X protein anomaly unaccompanied by detectable changes in the prothrombin level
or activity.