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Evaluation of the nature of mildly prolonged prothrombin times
Author(s) -
Mazzucconi M. G.,
Mariani G.,
Chistolini A.,
Lasagni R. Pasquali,
Motta M.,
Ghirardini A.,
Altieri D.,
Mannucci P. M.,
Mandelli F.
Publication year - 1987
Publication title -
american journal of hematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.456
H-Index - 105
eISSN - 1096-8652
pISSN - 0361-8609
DOI - 10.1002/ajh.2830240106
Subject(s) - heterozygote advantage , factor vii , asymptomatic , vitamin k deficiency , medicine , prothrombin complex , clotting factor , endocrinology , vitamin k , genetics , allele , coagulation , biology , gene
Twenty‐one asymptomatic individuals with a mildly prolonged prothrombin time ( > 2 SD from the prothrombin time of the reference plasma) were found to have a mild isolated factor VII (F VII) defect ( x 38.8 U/dl; SD 13.2). Factor VII antigen levels were also found to be reduced ( x 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 (1) the other vitamin K‐dependent clotting factors were normal; (2) the defect is transmitted throughout the kindred with the same mode of inheritance as F VII congenital deficiency; and (3) 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.