Test BackgroundUsually ordered as part of a thrombophilia screen. Protein C is a vitamin K-dependent protein that is synthesised in the liver. Hereditary and acquired protein C deficiencies are a known risk factor for venous thrombosis. Heterozygous deficiency of protein C has a prevalence of 1 in 300, the majority of whom are asymptomatic. Homozygous protein C deficiency presents with a form of disseminated intravascular coagulation in newborns (purpura fulminans). Protein S (PS) is a vitamin K-dependent plasma glycoprotein, synthesised in the liver and endothelial cells, that serves as the cofactor for the anticoagulant function of activated protein C (APC) in inactivating factors Va and Vllla. A hereditary or acquired deficiency of PS is associated with a thrombotic tendency. Protein S deficiency accounts for 2-3 % of thrombotic events. The age of onset of thrombosis is generally 10 to 50 years and rarely earlier than 10 years. Type I protein S deficiency (the most common deficiency) is a heterozygous state with a quantitative reduction in protein S levels. Protein S type II deficiencies have normal levels of protein S but a reduced activity – these are very rare. Type III deficiencies are more common than type II and have a normal total protein S level, but a reduced free protein S level.
Protein C 70-140 IU/dL
Sample Required 4 x 4.5 mL sodium citrate (pale blue top) adults4 x 1.8 mL sodium citrate (pale blue top) paediatrics
Turnaround Time 14 days
NotesSpecial handling: avoid prolonged stasis during venepuncture. Sample must be received by lab within 2 hours of collection. Please note: samples will be rejected if underfilled, clotted, haemolysed or if patients are receiving anticoagulant therapy. Similarly, sampling is inappropriate within 4 weeks post-childbirth or during an acute phase inflammatory response.