Complement C4 Level Assay

Complement C4 (MW: 188 kDa), a central complement component in the classical and lectin pathways, is required to generate C4b2a, the C3 convertase of the classical pathway. C4 is cleaved to C4a (anaphylatoxin; 8 kDa) and C4b (180 kDa). C4b binds C2, and after removal of non-catalytic domain on C2, the C4b2a complex is formed. Unlike plasma C3, plasma C4 levels are typically normal in aHUS and C3G, however this test helps to rule out other complement-mediated renal diseases.

Indications for screening
Testing is appropriate for patients with aHUS, DDD, and C3GN

MORL screening methodology
Turbidimetry-based method

Turnaround time
Turnaround time is ~ 2 weeks

Sample Required
1 ml frozen serum (Red top, see testing requisition (page 3) for specimen handling).

Cost & CPT Codes

• MORL Testing Menu
• Clinical Kidney Testing Requisition Form

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