INR is reflexed on patients with a low Protein C level.

3 to 5 days

Batched 2 times per week.

Non-coumadin anticoagulants may falsely elevate Protein C values, even when the concurrent PTT is normal.

Two 2.7 mL blood, LIGHT BLUE top tubes, 3.2% sodium citrate OR two 1 mL frozen sodium citrate plasma aliquots. Hemostasis & Thrombosis Lab sodium citrate specimens must be processed and frozen within 2 hours of specimen collection. Stability is 14 days at -70 C.

Draw volume is critical due to the liquid anticoagulant. Allow tubes to fill by vacuum.
• Tubes with rubber stopper: fill to line on label.
• Tubes with plastic (Hemogard) cap: the fill level is above the top of the label.
• Syringe: do not remove the vacutainer stopper. Insert the needle through the stopper and allow the tube to fill by vacuum. Do not overfill the vacutainer.
• Pediatric tubes have no vacuum. Remove the cap and add blood to the 1.3 mL mark. Do not overfill.

OHSU clinics must cab specimen to the H&T Lab, Dillehunt Hall, Room 3050 if processing is delayed or not possible on site. A phone call is helpful to alert the lab at 503-494-8445.

Detailed instructions are included in this manual under Specialized Lab Services, Hemostasis & Thrombosis (Opens in a new window) section.

Two full pediatric 1.3 mL LIGHT BLUE top tubes, 3.2% sodium citrate, OR two 0.5 mL frozen sodium citrate plasma aliquots. 

For pediatric patients requiring multiple coagulation tests, please call 503-494-7383 regarding draw volumes.

70% to 140%
For children less than 6 months, see link to published reference ranges (Opens in a new window).

This test aids in the diagnosis of patients at risk of venous thromboembolic disease.
Normal, full-term newborn infants or healthy premature infants may have decreased levels of protein C activity (15% to 50%), which may not reach adult levels until later in childhood or early adolescence.

Discontinue Coumadin therapy 1 month prior to testing. Heparin greater than 1.0 U/mL, coumadin, and fibrinolytic agents interfere with this assay. Coumadin decreases Protein C.

Methodology: Clot-based on prolongation of APTT assay.

High doses of standard heparin (greater than 1.0 U/mL) may interfere with a PT mixing study. Anti-Xa agents such as Rivaroxaban may also interfere with PT mixing studies. Clinical correlation is advised.

Protein C
PTC