A study of Protein S antigen levels in 3788 healthy volunteers: influence of age, sex and hormone use, and estimate for prevalence of deficiency state

Total Protein S (tPS) and free Protein S (fPS) antigen levels were measured in 3788 healthy blood donors, Men had higher levels of both parameters tha n women (P < 0.001). Age had no effect on tPS in men, although there was a slight reduction in fPS levels with increasing age. In women increasing age was associated with a significant increase in tPS levels (P < 0.001) but h ad no effect on fPS after adjustment for menopausal state. Oral contracepti ve pill (OCP) use significantly lowered tPS but had no effect on fPS, In po st-menopausal women, hormone replacement therapy (HRT) use had no statistic ally significant effect on either tPS or fPS, Donors with tPS or fPS levels in the lowest percentile (n = 56) were retested; only nine with repeat low levels were identified, eight of whom had persistently low levels over a 4 -7-year follow-up. Acquired deficiency was excluded. When possible, family studies were performed, leading to an estimate of prevalence of familial PS deficiency of between 0.03% and 0.13% in the general population.