INFLUENCE OF GENDER, AGE AND SAMPLING TIME ON PLASMA FIBRINOLYTIC VARIABLES AND FIBRINOGEN - A POPULATION STUDY

Reference data are provided for tissue plasminogen activator (t-PA) ac tivity, t-PA antigen levels, plasminogen activator inhibitor type 1 (P AI-1) activity and fibrinogen levels in plasma. The data are from a po pulation-based sample of 1288 healthy 25 to 64-year-old men and women who were not taking any medication. Time of sampling influenced the me asurements in that, from 07:00 to 14:00 t-PA activity rose, t-PA antig en levels and PAI-1 activity declined, whereas plasma fibrinogen level s remained unchanged. Age had little influence on t-PA activity or PAI -1 activity, although t-PA antigen levels correlated with increasing a ge (r=0.26 and 0.34, in men and women, respectively). Fibrinogen level s also correlated with age (r=0.29 in both sexes). In the 45 to 54-yea r age group, t-PA activity was significantly lower (p<0.001) and PAI-1 activity significantly greater (p < 0.01) in men than in women; other wise there were no gender differences in t-PA and PAI-1 activities. t- PA antigen levels were consistently greater in men up to the age of 55 . Fibrinogen levels were greater in women in the youngest and oldest a ge group. The strongest interrelations between the fibrinolytic variab les were observed between t-PA and PAI-1 activities (r=-0.73 in men, - 0.59 in women, p<0.001) and between PAI-1 activity and t-PA antigen le vels (r=0.40 in men, 0.37 in women, p<0.001). This first population-ba sed description of fibrinolytic parameters, including t-PA activity, i n healthy middle-aged people shows that timing of blood sampling shoul d be standardized and that reference data must be age- and sex-specifi c. In the assessment of fibrinolytic function, measurements of t-PA an tigen levels seem to add little to determinations of t-PA and PAI-1 ac tivities.