Evaluation of the nature of mildly prolonged prothrombin times

Am J Hematol. 1987 Jan;24(1):37-45. doi: 10.1002/ajh.2830240106.


Twenty-one asymptomatic individuals with a mildly prolonged prothrombin time (greater than 2 SD from the prothrombin time of the reference plasma) were found to have a mild isolated factor VII (F VII) defect (mean 38.8 U/dl; SD 13.2). Factor VII antigen levels were also found to be reduced (mean 45.5 U/dl; SD 7.8) in 13 of them. These figures were compared with those of 50 normals and 28 obligatory heterozygotes for F VII deficiency. The phenotypical behaviors in the propositi were found to be equal to those of the F VII congenital deficiency heterozygotes: the discrepant one (VII+) and the nondiscrepant one (VII-/R). Fifteen families of the propositi could also be studied, totalling 55 additional individuals; in 25 of them (ten pedigrees) a mild F VII deficiency was found showing the same phenotypical features of the corresponding propositi. We therefore believe that these individuals with mild F VII deficiency can be considered as heterozygotes for the defect, since the other vitamin K-dependent clotting factors were normal; the defect is transmitted throughout the kindred with the same mode of inheritance as F VII congenital deficiency; and F VII:C and F VII:Ag levels are highly comparable with those of known obligatory heterozygotes for F VII deficiency. On the grounds of a careful statistical analysis we propose a formula which allows a discrimination between the two phenotypes of the heterozygotes for F VII congenital deficiency. In addition it is suggested that sensitive tissue thromboplastins should be used to pick up these mild defects.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Antigens / analysis
  • Child
  • Child, Preschool
  • Factor VII / analysis
  • Factor VII / immunology
  • Factor VII Deficiency / blood
  • Genetic Variation
  • Heterozygote
  • Humans
  • Middle Aged
  • Phenotype
  • Prothrombin Time*
  • Thromboplastin


  • Antigens
  • factor VII clotting antigen
  • factor VII related antigen
  • Factor VII
  • Thromboplastin