C3 Nephritic Factor
Test Code
C3NF
Description
C3 nephritic factors (C3NF) are autoantibodies that bind to and stabilize the C3 convertase (C3bBb) of the complement alternative pathway. C3 convertase stabilization leads to prolonged and\or dysregulated complement activity. C3NF positivity often leads to low serum levels of C3 with normal C4 levels. C3NFs are associated with kidney diseases including C3 glomerulopathy (C3G) and immune complex-associated-membranoproliferative glomerulonephritis (IC-MPG), as well as autoimmune disorders such as systemic lupus erythematosus and acquired partial lipodystrophy.
Collect
Serum from a plain red top is the only acceptable sample type. Gel barrier tubes are not acceptable.
Patient Prep
Allow serum to clot at room temperature for 30 - 60 minutes after venipuncture, then 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 tube and immediately store samples at – 60°C or below in an ultra-low freezer.Preferred volume: 1 mL
Ambient temperature for centrifugation is acceptable provided that the time between collection and storage is minimized (approximately 60 minutes).
Pediatric Collection
Minimum volume: 0.5 mL serum, frozen
Unacceptable Conditions
Thawed specimen or specimens stored at room temperature prior to shipment.
Storage Transport Temp
Send frozen serum Priority Overnight via FedEx and in a well insulated container on dry ice.
Stability
-60°C or below in an ultra-low freezer - up to 1 year
Notes
This is not a direct measurement of antibody quantity but only a qualitative (indirect) measure of its activity to produce C3b from full length C3. Additional testing time may be needed for less than perfect samples or confirmatory/reflex testing.Performed
Monday - Friday
Methodology
Immunofixation Electrophoresis
Turnaround Time
14 Business days
Department
Complement Lab
Synonyms
Complement (C3 Nephritic Factor), 2-D Immunoelectrophoresis (C3 Nephritic Factor)
Study Offerings
CAP/CLIA
Reference Interval
Normal – Ratio is 0 – 0.26
Equivocal – Ratio is 0.27 – 0.33
Positive – Ratio is > 0.34
Interpretation
C3NF positivity could be a potential driver of complement alternative pathway dysregulation.CPT Code
86161
New York Approved
Legacy
FDA
LDT