C2 Complement, Functional with Reflex, Serum
Test Mnemonic
C2COM
CPT Codes
- 86161 - QTY (1)
Aliases
- C2 Functional
Includes
- Complement C2
- Complement C3, if indicated
- Complement C4, if indicated
Performing Laboratory
Mayo Clinic Dpt of Lab Med & Pathology
Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 1 mL | Serum | SST (Gold) | Place specimen on ice after draw. | Frozen, Critical | Fasting preferred. Place tube on wet ice immediately after collection and allow specimen to clot. Separate serum from cells and transfer to standard aliquot tube. Freeze immediately. |
Alternate Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 1 mL | Serum | No additive (Red) | Place specimen on ice after draw. | Frozen, Critical | Fasting preferred. Place tube on wet ice immediately after collection and allow specimen to clot. Separate serum from cells and transfer to standard aliquot tube. Freeze immediately. |
Minimum Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 0.5 mL |
Stability
| Environmental Condition | Description |
|---|---|
| Frozen | 21 days |
| Ambient | Unacceptable |
| Refrigerated | Unacceptable |
Days Performed
Mon - Fri
Turnaround Time
2 - 4 days
Methodology
| Name | Description |
|---|---|
| Turbidimetry (TURB) |
Special Info
Testing Algorithm: If the C2 result is < 15 U/mL, then C3 and C4 will be performed at an additional cost. Grossly lipemic specimens are unacceptable.
Clinical Info
The classic pathway of the complement system is composed of a series of proteins that are activated in response to the presence of immune complexes. This activation process results in the formation of the lytic membrane attack complex, as well as the generation of activation peptides that are chemotactic for neutrophils and that bind to immune complexes and complement receptors. The absence of early components (C1, C2, C4) of the complement cascade results in the inability of immune complexes to activate the cascade. Patients with deficiencies of the early complement proteins are unable to generate lytic activity or to clear immune complexes. Although rare, C2 deficiency is the most common inherited complement deficiency. Homozygous C2 deficiency has an estimated prevalence ranging from 1 in 10,000 to 1 in 40,000. Half of the homozygous patients are clinically normal. However, discoid lupus erythematosus or systemic lupus erythematosus (SLE) occurs in approximately one-third of patients with homozygous C2 deficiency. Patients with SLE and a C2 deficiency frequently have a normal anti-ds DNA titer. Clinically, many have lupus-like skin lesions and photosensitivity, but immunofluorescence studies may fail to demonstrate immunoglobulin or complement along the epidermal-dermal junction. Other diseases reported to be associated with C2 deficiency include dermatomyositis, glomerulonephritis, vasculitis, atrophodema, cold urticaria, inflammatory bowel disease, and recurrent infections. The laboratory findings that suggest C2 deficiency include a hemolytic complement (CH50) of nearly zero, with normal values for C3 and C4.
Reflex Tests
The following additional test(s) may be ordered depending on results: