Summary
To assess variations of coagulation factors in women, 123 women were included in a
cross-sectional study of the effect of age, ethnic origin, blood group and menstrual
cycle on surface induced coagulation time (activated partial thromboplastin time)
and plasma levels of Factor VIII clotting assay, von Willebrand factor antigen, von
Willebrand factor activity and factor XI. The effect of menstrual cycle was further
assessed in a longitudinal study including 39 Caucasian women, 20 of whom were using
combined oral contraceptives. Activated partial thromboplastin time was longer in
women with blood groups B or O, and plasma levels of factor VIII clotting assay, von
Willebrand factor antigen and von Willebrand factor activity were significantly higher
in black women. Fibrinogen, von Willebrand factor antigen and von Willebrand factor
activity concentrations showed strong cyclic variations with peak values in the luteal
phase. This pattern was dampened for von Willebrand factor antigen and von Willebrand
factor activity but completely disappeared for fibrinogen with the use of combined
oral contraceptives. There was a cyclical pattern for factor VIII clotting assay in
pill users, evidence of which was not evident in non-pill users. There were strong
associations between the levels of von Willebrand factor antigen and von Willebrand
factor activity and age, with levels rising by an average of 0.17 and 0.15 U/ml, respectively,
for each 10 year increase in age. In conclusion, there are great inter- and intraindividual
variations in coagulation markers in women due to different physiological conditions
such as age, ethnicity, blood group and phases of the menstrual cycle. However, there
were no significant associations between coagulation markers and weight, alcohol consumption
or smoking status.
Keywords
Coagulation factors - variability - menstrual cycle - ethnicity - combined oral contraceptives
