Factor B Function
Test Code
FBF
Description
The complement system is part of our innate immune response. It is vital to our defense against invasive microorganisms. Complement activation can occur through the classical, lectin and alternative pathway, which then converge to a common terminal pathway. Complement deficiency can lead to life-threatening infections as well as long-term autoimmune conditions such as systemic lupus erythematosus (SLE) and hereditary angioedema (HAE).
The factor B hemolytic assay is a sensitive method for detection of the alternative complement pathway factor B protein activity or lack thereof. Severe or recurrent infections that produce strong activation of the alternative complement pathway can lead to low factor B protein levels and reduced factor B activity. Low or absent factor B activity is also observed with genetic deficiencies of factor B that lead to a lack of or insufficient production of factor B protein. Low factor B activity can be associated with low AH50 activity.
Collect
Serum from a Red top tube is the only acceptable sample type. The collection tube should be completely filled with blood. Invert tube several times to initiate the clotting process. Keep the tube filled with blood at room temperature for 30-60 minutes to allow the blood to clot.
Patient Prep
Centrifuge the collection tube at 1600 (± 200) x g (rcf) at 4°C (± 2°C) for 15 (±1) minutes. Transfer the cell-free serum to a clean cryogenic storage tube and immediately store the cryogenic tube at -60°C or below in an ultra-low freezer.
Preferred volume: 1.0 mL serum
Minimum volume: 0.5 mL serum
Pediatric Collection
Minimum volume: 0.5 mL serum
Unacceptable Conditions
Thawed samples or samples stored at room temperature prior to shipment.
Storage Transport Temp
Ship samples overnight in a well-insulated container on dry ice.
Stability
-60°C or below in an ultra-low freezer - up to 2 years
Notes
Additional testing may be needed for less than perfect samples on confirmatory testing/reflex testing.
To prevent unnecessary delays in testing, please send one aliquot per test request.
Performed
Monday - Friday
Methodology
Hemolytic Assay
Turnaround Time
up to 4 weeks
Department
Complement Lab
Synonyms
Complement (Factor B Function), Functional Properdin Factor B, Hemolytic assay (Factor B function), PFBF
Study Offerings
Not offered
Related Tests
Alternative Complement Pathway Activity (AH50), Factor B Level
Reference Interval
123 - 426 Units/mL
Interpretation
Reduced factor B function could be indicative of an immunodeficiency, an autoimmune disease or an active infection.
CPT Code
86161
New York Approved
No: Run with Waiver
FDA
LDT