Home
HelpTest Code C5AG C5 Complement, Antigen, Serum
Reporting Name
C5 Complement, Antigen, SUseful For
Diagnosis of C5 deficiency
Investigation of a patient with an absent total complement (CH50) level
Method Name
Nephelometry
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
SerumOrdering Guidance
The total complement assay (COM / Complement, Total, Serum) should be used as a screen for suspected complement deficiencies before ordering individual complement component assays. A deficiency of an individual component of the complement cascade will result in an undetectable total complement level.
Specimen Required
Patient Preparation:
Fasting: 12 hours, preferred but not required
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Collection Container/Tube:
Preferred: Red top
Acceptable: Serum gel
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL Serum
Collection Instructions: Centrifuge and aliquot serum into a plastic vial.
Specimen Minimum Volume
Serum: 0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum | Frozen (preferred) | 60 days |
| Refrigerated | 28 days | |
| Ambient | 7 days |
Reject Due To
| Gross hemolysis | OK |
| Gross lipemia | Reject |
| Gross icterus | OK |
Reference Values
10.6-26.3 mg/dL
Day(s) Performed
Tuesday, Friday
CPT Code Information
86160
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| C5AG | C5 Complement, Antigen, S | 4505-4 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| C5AG | C5 Complement, Antigen, S | 4505-4 |
Clinical Information
Complement proteins are components of the innate immune system. There are 3 pathways to complement activation: the classic pathway, the alternative (or properdin) pathway, and the lectin activation (mannan-binding protein: MBP) pathway. 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. The activation process results in the generation of peptides that are chemotactic for neutrophils and that bind to immune complexes and complement receptors. The end result of the complement activation cascade is the formation of the lytic membrane attack complex (MAC). More than 30 cases of C5 deficiency have been reported. Most of these patients have neisserial infections.
The C5 antigen test measures the concentration of C5 and is used to study complement component 5 deficiency. If a patient is being treated with eculizumab or another C5 inhibitor, the concentration of C5 may be elevated, as the reagents in this immunoassay cannot distinguish between free C5 and C5 bound to a C5 inhibitor. Testing for alternative pathway function or specifically for C5 function will provide more insight into whether the C5 is free, particularly if the goal of testing is therapeutic drug monitoring for a C5 inhibitor.