Measurement of fibrinogen-fibrin-related antigen in serum as aid to diagnosis of deep vein thrombosis in outpatients.

A study of serum levels of fibrinogen-fibrin-related antigen (F.R.-antigen) in outpatients presenting with clinical features suggesting deep vein thrombosis was undertaken. A raised serum level of this antigen (greater than 12 mg/1) is strong evidence in favour of the diagnosis of deep vein thrombosis. It is virtually conclusive evidence if other known causes of a raised level of the antigen are absent. On the other hand, a normal serum level of F.R.-antigen does not exclude even extensive thrombosis, and other objective techniques are required to substantiate the diagnosis.