Test Overview
Test Methodology

Radial Immunodiffusion

Test Usage

Decreased values are seen when the alternate pathway of complement is activated.

Reference Range *

127.6 - 278.5 mcg/mL

* Reference ranges may change over time. Please refer to the original patient report when evaluating results.

Test Details
Analytic Time

4 weeks

Soft Order Code
  • Factor B level by RID
  • PFB
  • Complement (C3) Proactivator
  • Complement (C3) PA
  • Complement (C3) Activator
Reference Laboratory
Mayo Wild 85 (ZW85) (National Jewish Health FBL)
Special Testing
Specimen Requirements
Collection Instructions

Collect specimen in a lavender top tube. Centrifuge, aliquot plasma into a plastic vial within 30 minutes of collection, and freeze.

Normal Volume
1 mL EDTA plasma
Minimum Volume
0.5 mL EDTA plasma
Additional Information

Activation via the alternate pathway is facilitated by particulate surfaces such as bacterial cell walls or complex polysaccharides. Alternate pathway activation is associated with nonimmune events. Decreased levels of PFB together with a decrease in serum C3 are indicative of significant and prolonged alternate pathway activation of complement. Test sent to Mayo Medical Laboratories; performed by National Jewish Health.

CPT Code
Fee Code