| Description: |
Protein S is a vitamin K-dependent co-factor for activated protein C, which serves to inactivate factors Va and VIIIa. Protein S deficiency is clinically indistinguishable from protein C deficiency, with heterozygous individuals at an increased risk of recurrent venous thrombosis. The assay is useful for evaluation of thrombophilic patients, in particular those who have a family history of thrombosis, thrombosis at a young age (<40 years), recurrent thrombosis or thrombosis at unusual sites (inferior vena cava, mesenteric veins). Normal neonates have lower protein S levels than adults do. Pregnancy normally results in decreased protein S levels. Patients with the factor V Leiden mutation may have artificially low functional Protein S levels. Protein S is a vitamin K-dependent protein, so warfarin use will result in low levels. |
