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

Routine: 1 Day
Urgent: N/A

Activities are batched daily 7 days a week. Inhibitors are batched twice per week.

3.2% 2 to 2.7 mL blood in a LIGHT BLUE top tube, 3.2% sodium citrate.

3.2% sodium citrate tubes are acceptable when they are filled to the line on the manufacturers label. Tubes must be full (see comments below). For referral testing, submit 3 tubes of 1.0 mL platelet poor plasma.

Sodium citrate specimens must be processed and frozen within 2 hours of specimen collection.

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 instructions are under Hemostasis & Thrombosis section (Opens in a new window).

Sodium citrate tubes are acceptable when they are filled to the line on the manufacturers label.

One 2.7 mL correctly filled in an adult size LIGHT BLUE top tube, or two correctly filled 1.3 mL pediatric BLUE top tubes, 3.2% sodium citrate.

A single 1.3 mL pediatric tube may be sent but will only allow for factor activity testing; the inhibitor, if indicated, may not be performed due to insufficient plasma volume.

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

Reference Range: 65% to 150%
Inhibitor: Less than 0.6 BU

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.

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

Inhibitors to factor IX arise in about 3% of persons with severe hemophilia B, which is less common that the incidence of inhibitors to factor VIII in persons with severe hemophilia A. In both types of hemophilia, most inhibitors arise early in life, after only a few injections of the missing clotting factor.

Inhibitors to factor IX are sometimes more dangerous than those to factor VIII. The reaction between factor VIII and its inhibitor-antibody does not cause symptoms. The reaction between factor IX and its inhibitor-antibody may cause severe allergic reactions which can be life-threatening (so-called "anaphylactic reactions"). Such reactions may occur with the very first infusion of factor IX after an inhibitor has developed - before anyone is aware that an inhibitor has arisen. All inhibitors in hemophilia B do not cause allergic reactions on exposure to more factor IX. Development of an inhibitor to factor IX can be predicted, at least in part, by determining the kind of factor IX gene mutation the baby has.

Methodology: clotting, Bethesda assay.

Factor 9
Inhibitor
FIX