Summary
Functional antithrombin III levels were measured by factor Xa inhibition in 63 members
of a large family with type 2 antithrombin III deficiency and individuals were classified
as antithrombin III deficient or non-deficient according to the results. FI+2 and
TAT complexes were measured using an ELISA and FPA levels were measured by radioimmunoassay.
Thirty subjects (48%) were classified as antithrombin III deficient and 33 (52%) as
antithrombin III non-deficient. The mean level of FI+2 was significantly higher in
the deficient adults (0.87 ± 0.26) compared to both the non-deficient adults (0.70
± 0.21) (p = 0.03) and the deficient adults receiving warfarin (0.16 ± 0.01) (p <0.001). The differences in the mean values of TAT complexes and FPA between deficient
and non-deficient individuals were not statistically significant.
These findings suggest that untreated antithrombin III deficient subjects generate
more thrombin than their non-deficient family members and that warfarin inhibits this
thrombin formation. In this cross-sectional study, it is not possible to correlate
the levels of the surrogate makers with future clinical outcome.
