TEST CATALOG ORDERING & RESULTS SPECIMEN HANDLING CUSTOMER SERVICE EDUCATION & INSIGHTS
Test Catalog

Test ID: 9INHE    
Factor IX Inhibitor Evaluation, Plasma

Useful For Suggests clinical disorders or settings where the test may be helpful

Detection and titering of coagulation inhibitor to the specific factor requested, primarily factor IX in patients with hemophilia B

 

This test is not useful for the detection of a lupus-like circulating anticoagulant inhibitor, a nonspecific circulating anticoagulant, or other inhibitors that are not specific for coagulation factors.

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

Testing begins with coagulation factor IX activity assay with dilutions to evaluate assay inhibition; if the factor IX activity assay is normal or increased, then a technical interpretation will be provided.

 

If the factor IX activity assay is decreased, then an inhibitor screen will be performed at an additional charge to look for specific factor IX inhibition and a professional interpretation will be provided. If specific inhibition is apparent, the titer of the inhibitor will be determined.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Factor IX inhibitors arise in patients with severe hemophilia B after factor IX transfusion. Patients with factor IX inhibitors may also develop anaphylactic reactions in response to factor IX infusions. Acquired factor IX inhibitors, occurring in previously healthy people, are exceedingly rare.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

FACTOR IX ACTIVITY ASSAY

Adults: 65-140%

Normal, full-term newborn infants or healthy premature infants may have decreased levels (> or =20%), which may not reach adult levels for > or =180 days postnatal.*

*See Pediatric Hemostasis References section in Coagulation Guidelines for Specimen Handling and Processing in Special Instructions.

Interpretation Provides information to assist in interpretation of the test results

Normally, there is no inhibitor (ie, negative result).

 

If the screening assays indicate the presence of an inhibitor, it will be quantitated and reported in Bethesda (or equivalent) units.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Occasionally, a potent lupus-like anticoagulant may cause false-positive testing for a specific factor inhibitor (eg, factor VIII or IX). See Ordering Guidance.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Hoffman R, Benz Jr EJ, Silberstein LE, et al, eds: Hematology: Basic Principles and Practice. 7th ed. Elsevier; 2018

2. Chitlur M, Warrier I, Rajpurkar M, et al: Inhibitors in factor IX deficiency a report of the ISTH-SSC international FIX inhibitor registry (1997-2006). Haemophilia. 2009;15(5):1027-1031. doi: 10.1111/j.1365-2516.2009.02039.x

Special Instructions Library of PDFs including pertinent information and forms related to the test