The effect of plasma caeruloplasmin levels on the sensitivity for activated protein C

Summary. The effect of caeruloplasmin levels on the sensitivity for activated protein C (APC), measured by a clotting assay based on the activated partial thromboplastin time, was investigated in a large group of healthy individuals without factor V Leiden. A modest inverse association between caeruloplasmin and normalized APC sensitivity ratio was found (regression coefficient β = −0·33 × 10 −2 ; 95% confidence interval, −0·42 × 10 −2 to −0·24 × 10 −2 ). After adjustment for sex and oral contraceptive use, this association weakened (β = −0·19 × 10 −2 ; 95% CI: −0·34 × 10 −2 to −0·05 × 10 −2 ). After additional adjustment for factor VIII levels, which are known to influence the assay, the effect of caeruloplasmin on APC sensitivity completely disappeared.