DEPARTMENT: SPECIAL COAGULATION
DIRECTOR: James Zehnder, M.D.
NEW TESTS: Protein C and Protein S Antigen
Test Description and Clinical Indications:
Protein C is a natural anticoagulant produced
in the liver. It is vitamin K dependent and requires thrombin and thrombomodulin for activation.
Activated protein C in the presence of cofactor protein S inactivates factors Va and VIIIa, thereby
limiting coagulation. Patients heterozygous for deficiency of protein C or S may exhibit recurrent
venous thrombosis at a young age (peak incidence between ages 15 and 40). Heterozygotes also
appear to have an increased risk of coumadin-induced skin necrosis. Patients homozygous for
protein C deficiency present with generalized microvascular thrombosis in the neonatal period (purpura fulminanas). Normal neonates have lower levels of protein C than adults. Warfarin therapy
will result in low protein C levels. See also Thrombosis screen and Activated Protein C Resistance in
the Test Directory at www.stanfordlab.com.
Protein S is a vitamin K-dependent cofactor 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 artifactually low functional Protein S levels. Protein S is a vitamin K-dependent protein, so warfarin use will result in low levels.
Protein C Antigen, Total |
Order Code: TOTALC |
| |
|
Specimen Type: |
Platelet Poor Plasma, Frozen (2 aliquots) |
Container Type: |
Light-blue-top tube (sodium citrate) |
Required Volume: |
5 mL |
Minimum Volume (Pediatric): |
Full tube (2.7 mL blood or 1.8 mL blood depending on size of tube used) |
Special Handling: |
Within 1 hour of collection, centrifuge tube as required to obtain platelet-poor plasma. Aliquot platelet-poor plasma into plastic tubes (minimum 2 aliquots). Freeze immediately. Transport frozen. |
Methodology: |
Manual method by ELISA |
TAT: |
5-7 days |
CPT Codes: |
85302 |
Report: |
% |
| Causes For Rejection: |
Clotted, hemolyzed, not received within 1 hour from draw; Hct >55% (must be drawn in special tube obtained from Coagulation Laboratory); improper volume in tube |
Protein S Antigen, Total |
Order Code: TOTALS |
| |
|
Specimen Type: |
Plasma |
Container Type: |
Light-blue-top tube (sodium citrate) |
Required Volume: |
5 mL |
Minimum Volume (Pediatric): |
Full tube (2.7 mL blood or 1.8 mL blood depending on size of tube used) |
Special Handling: |
Within 1 hour of collection, centrifuge tube as required to obtain platelet-poor plasma. Aliquot platelet-poor plasma into plastic tubes (minimum 2 aliquots). Freeze immediately. Transport frozen. |
Methodology: |
Automated Latex Immunoassay |
TAT: |
5-7 days |
CPT Codes: |
85305 |
| Report: |
% |
Causes For Rejection: |
Clotted, hemolyzed, not received within 1 hour from draw; Hct >55% (must be drawn in special tube obtained from Coagulation Laboratory); improper volume in tube |
Protein C and S, Total Combined |
Order Code: CSTOTL |
| |
|
Specimen Type: |
Plasma |
Container Type: |
Light-blue-top tube (sodium citrate) |
Required Volume: |
10 mL |
Minimum Volume (Pediatric): |
Full tube (2.7 mL blood or 1.8 mL blood depending on size of tube used) |
Special Handling: |
Within 1 hour of collection, centrifuge tube as required to obtain platelet-poor plasma. Aliquot platelet-poor plasma into plastic tubes (minimum 2 aliquots). Freeze immediately. Transport frozen. |
Methodology: |
Manual method by ELISA; Automated Latex Immunoassay |
Components: |
Protein C Antigen, Total; Protein S Antigen, Total |
TAT: |
5-7 days |
CPT Codes: |
85302, 85305 |
| Report: |
% |
Causes For Rejection: |
Clotted, hemolyzed, not received within 1 hour from draw; Hct >55% (must be drawn in special tube obtained from Coagulation Laboratory); improper volume in tube |
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