The logistic regressionmodel (Table 3) enables identification
of the marginal contribution of the above determinants
to the risk of seropositivity, both total and recent infection.
Age increased the risk of syphilis in the given population
of blood donors (controlling for the other variables in the
model). Every additional year of age adds 6% to the risk of
either total seropositivity or recent infection (odds ratio =
1.06,