Evaluation of the nature of mildly prolonged prothrombin times

M. G. Mazzucconi, G. Mariani, A. Chistolini, R. P. Lasagni, M. Motta, A. Ghirardini, D. Altieri, P. M. Mannucci, F. Mandelli

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Abstract

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 (x̄ 38.8 U/dl; SD 13.2). Factor VII antigen levels were also found to be reduced (x̄ 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.

Original languageEnglish
Pages (from-to)37-45
Number of pages9
JournalAmerican Journal of Hematology
Volume24
Issue number1
DOIs
Publication statusPublished - 1987

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ASJC Scopus subject areas

  • Hematology

Cite this

Mazzucconi, M. G., Mariani, G., Chistolini, A., Lasagni, R. P., Motta, M., Ghirardini, A., Altieri, D., Mannucci, P. M., & Mandelli, F. (1987). Evaluation of the nature of mildly prolonged prothrombin times. American Journal of Hematology, 24(1), 37-45. https://doi.org/10.1002/ajh.2830240106