Complement Component 2
Ordering Recommendation
Follow-up test for complement activity screening when CH50 is low or absent and AH50 is normal and high suspicion remains for complement deficiency.
Submit With Order
Quantitative Radial Immunodiffusion
Mon, Thu
5-10 days
New York DOH Approval Status
This test is New York DOH approved.
Specimen Required
Patient Preparation
Serum separator tube.  
Specimen Preparation
Allow specimen to clot for one hour at room temperature. Separate serum from cells ASAP or within 2 hours of collection. Transfer 1 mL serum to an ARUP Standard Transport Tube and freeze immediately. (Min: 0.3 mL)  
Storage/Transport Temperature
CRITICAL FROZEN. Separate specimens must be submitted when multiple tests are ordered.  
Unacceptable Conditions
Non-frozen specimens. Specimens exposed to repeated freeze/thaw cycles. Specimens left to clot at refrigerated temperature.  
After separation from cells: Ambient: 2 hours; Refrigerated: Unacceptable; Frozen: 2 weeks  
Reference Interval
1.0-4.0 mg/dL
Interpretive Data
Decreased C2 levels may be associated with increased susceptibility to infection (especially pneumococcal infections), systemic lupus erythematosus-like disease, rashes, arthritis, nephritis, and with C1-Esterase deficiency. Increased C2 levels are associated with the acute phase response.

See Compliance Statement D:
CPT Code(s)
Component Test Code*Component Chart Name
0050148Complement Component 2
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.
Cross References
  • C2
  • C2 Antigen
  • C2 Level
  • Classical Pathway - Complement
  • complement classical pathway
  • Second componenet of complement