Protein C and S Activity with Reflex to Protein C and/or S Antigen

Casandra

Casandra Test Code QD36399Version 1 (DRAFT)

Performing Lab

Lab Quest DiagnosticsLab Test ID 7942CPT Codes 85303, 85306

Protein C and S Activity with Reflex to Protein C and/or S Antigen

Also known as: PC Activity, PC Antigen, Protein S Functional, PS Activity, PS Antigen

Clinical Use

Order Test

Use

Aids in evaluation of protein C (PC) and protein S (PS) deficiencies, which are associated with increased thrombotic risk. Deficiencies may be congenital or acquired, and acquired causes include vitamin K deficiency, liver disease, malignancy, DIC, surgery, trauma, or neonatal hepatic immaturity. Protein S deficiency may also be physiologic in pregnancy.

Special Instructions

Submit a separate, frozen vial for each special coagulation assay ordered. Draw blood in a light blue-top tube containing 3.2% sodium citrate, mix gently by inverting 3–4 times. Centrifuge 15 minutes at 1500 g within one hour of collection, then remove plasma carefully, avoiding buffy coat, and re-centrifuge to obtain platelet‑poor plasma. Freeze immediately and transport on dry ice or frozen. Room temperature and refrigerated specimens are unacceptable; frozen stability up to 14 days.

Limitations

Anticoagulant interference: Therapeutic warfarin may decrease activity; heparin (UFH or LMWH) may have no effect or falsely increase activity at higher levels; dabigatran or argatroban may falsely increase activity; factor Xa inhibitors (rivaroxaban, apixaban, edoxaban) may falsely increase activity.

Test Details

Methodology

Other

Biomarkers

4 targets

Protein C, ActivityProtein C, AntigenProtein S Antigen, TotalProtein S, Activity

Result Turnaround Time

Not provided.

Specimen

Plasma

Volume

Draw two light blue-top (sodium citrate) tubes, desired specimen volume: 4 mL (2 mL per aliquot)

Minimum Volume

Not provided

Container

Light Blue Top (Sodium Citrate)

Collection Instructions

Collect two sodium citrate tubes; mix by inverting 3‑4 times. Centrifuge 15 min at 1500 g within 1 h, transfer platelet‑poor plasma into two separate clear aliquot tubes (2 mL each), freeze immediately.