Factor B Autoantibodies (FBAA)

  • Dense Deposit Disease (DDD, aka Membranoproliferative Glomerulonephritis Type II, MPGNII)
  • C3 Glomerulonephritis (C3GN)
  • Atypical Hemolytic Uremic Syndrome (aHUS)

Factor B autoantibodies (FBAAs) have been associated with DDD (Strobel, et al. 2010; Chen, et al. 2011). FBAA binds to factor B and/or the individual component Bb part of C3 convertase. More importantly, FBAA enhances C3 convertase activity, which often leads to increased complement breakdown products. FBAA represents an additional acquired driver of disease in DDD, C3GN and aHUS. Although rare, FBAAs should be considered in the comprehensive evaluation of patients with DDD, C3GN and aHUS.

Indications for screening
Screening is appropriate in patients with aHUS and biopsy-proven DDD and C3GN.

MORL screening methodology
Enzyme Linked Immuno-Sorbent Assay (ELISA)

Turnaround time
~4 weeks

Sample Required
1 ml frozen serum (see Testing Requisition for specimen handling)

Cost & CPT Codes

The Clinical Diagnostics Service of the Molecular Otolaryngology & Renal Research Laboratories is a CLIA-approved, Joint Commission-accredited diagnostic laboratory.


Strobel, S., et al..: Anti-Factor B autoantibody in Dense Deposit Disease. Mol Immunol. 2010 Apr; 47(7-8):1476-83.
PubMed ID: 20193965

Chen, Q., et al..: Combined C3b and factor B autoantibodies and MPGN type II. N Engl J Med. 2011 Dec; 465(24):2340-23.
PubMed ID: 22168663