If factor activity level is less than 40%, an inhibitor test will be performed.

3 to 5 days

Batched once weekly.

Two full 2.7 mL LIGHT BLUE top tubes, 3.2% sodium citrate. 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 specimens to the Core Lab, Hatfield Research Center (HRC), Room 9D05 if processing is delayed or not possible on site. A phone call is helpful to alert the lab at 503-494-5764.

Detailed specimen collection and processing instructions are located under Lab Sections and then the Hemostasis and Thrombosis (Opens in a new window) section.

For referral testing, submit three tubes, each with 1.0 mL frozen platelet poor citrated plasma.

One full adult-sized 2.7 mL LIGHT BLUE top tube, 3.2% sodium citrate. Hemostasis & Thrombosis Lab sodium citrate specimens must be processed and frozen within 2 hours of specimen collection. Stability is 14 days at -70 C.

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

Inhibitor: Less than 0.6 BU.
Factor XI: 65% to 150%
For children less than 6 months, see link to published reference ranges (Opens in a new window).

Avoid warfarin (Coumadin) therapy for two weeks and heparin therapy for 2 days prior to the test.

Factor 11, Inhibitor
FXI