Protein C and Protein S

General

Synonym/Acronym:
protein C activity or protein C functional; protein C antigen; protein S antigen, free.

Rationale
To assess coagulation function and assist in diagnosis of disorders such as thrombosis related to protein C and protein S deficiency.

Patient Preparation
There are no food, fluid, or activity restrictions unless by medical direction. Patients should discontinue warfarin therapy for 2 wk prior to specimen collection, as ordered. Specimen collection should not be performed sooner than 10 days following a thrombotic or clotting event.

Normal Findings

Age Protein C Activity or Functional Protein C (Method: Electromagnetic Mechanical Clot Detection) Age Protein C Antigen (Method: Enzyme Immunoassay)
Neonate17%–53%Neonate17%–53%
1 wk–3 mo20%–65%1 wk–3 mo20%–65%
3–6 mo28%–80%3–6 mo28%–80%
6 mo–1 yr37%–81%6 mo–1 yr37%–81%
1–6 yr40%–90%1–6 yr40%–90%
7–11 yr68%–140%7–11 yr45%–93%
12–13 yr65%–160%12 yr–adult63%–153%
14–17 yr70%–170%
18 yr–adult83%-168%
Values are significantly reduced in children because of liver immaturity. Functional protein C and free protein S antigen, free are recommended for initial screening of protein C and protein S deficiency. The two are initially tested together because a deficiency in protein S may affect protein C activity. Protein C antigen is used to further distinguish inherited type 1 from inherited type 2 protein C deficiency.
Age Protein S Free Antigen (Method: Microlatex Particle-Mediated Immunoassay) Age Protein S Activity or Functional Protein S (Method: Electromagnetic Mechanical Clot Detection) Age Protein S Total Antigen (Method: Enzyme Immunoassay)
Newborn–3 mo15%–55%Newborn–3 mo15%–55%Newborn12%–60%
3–6 mo35%–90%3–6 mo35%–90%1 wk–29 day25%–80%
7–12 mo45%–115%7–12 mo45%–115%1–89 day30%–95%
1–5 yr60%–120%1–5 yr60%–120%3 mo–5 yr55%–120%
6–9 yr60%–130%6–13 yr60%–150%6–10 yr40%–115%
10–17 yr60%–140%14–17 yr50%–145%11 yr–adult male85%–135%
18 yr–adult male75%–145%18 yr–adult male70%–140%11 yr–adult female65%–130%
18 yr–adult male55%–125%18 yr–adult female60%–130%
Values are significantly reduced in children because of liver immaturity; levels reach normal adult levels within 3 to 6 mo of age. Protein S free antigen or functional protein S may be used to identify protein S deficiency. Protein S total antigen is used to further distinguish inherited types I, II, or III protein S deficiency.


Critical Findings and Potential Interventions
N/A

There's more to see -- the rest of this topic is available only to subscribers.