Conditions resulting in an acquired deficiency of both protein S and protein C:
(1) neonatal period
(2) vitamin K deficiency
(3) liver disease
(4) DIC
(5) acute thrombosis
(6) warfarin therapy
(7) L-asparaginase therapy
Conditions resulting in an acquired deficiency of protein S:
(1) chronic inflammatory states
(2) pregnancy
(3) estrogen therapy
Conditions resulting in an acquired deficiency of protein C:
(1) chemotherapy with cyclophosphamide, methotrexate, and/or 5-fluorouracil
Testing for a hereditary deficiency of protein S or protein C should be delayed until after the patient has recovered from any of the above conditions or any of the above treatments have been discontinued.
A patient being treated with warfarin can have plasma levels of protein S and C measured using the following protocol:
(1) Start heparin or low molecular weight heparin therapy.
(2) Discontinue the warfarin therapy.
(3) Wait 2 weeks before drawing the blood samples.
(4) Restart the warfarin therapy.
(5) Discontinue the heparin therapy after the warfarin therapy has been fully implemented.
