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# A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
C2 Complement, Functional, with Reflex, Serum (C2)
Test Code: C2SO
Synonyms/Keywords
C2 Functional
Test Components

If the C2 result is <15 U/mL, then C3 and C4 will be performed at an additional charge.

Useful For
The investigation of a patient with a low (absent) hemolytic complement (CH50), with reflex testing to C3 and C4, if appropriate.
Specimen Requirements
Fasting Required Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)
Pediatric Minimum Volume
(no repeat)
8 hour fast preferred (not required)​ ​Serum ​Red Top Tube (RTT) ​1 mL ​0.5 mL
Collection Processing Instructions
Immediately after drawing the specimen, place the tube on wet ice. Spin down and separate serum from clot. Immediately freeze serum specimen.
Specimen Stability Information
Specimen Type Temperature Time
Serum​ ​Frozen ​21 days
Rejection Criteria
Gross lipemia
Interference
As with all complement assays, proper sample handling is of utmost importance to ensure that the complement system is not activated before clinical testing.
 
Absent (or low) C2 functional levels in the presence of normal C2 antigen levels should be replicated with a new serum specimen to confirm that C2 inactivation has not occurred during shipping.
Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
Mayo Medical Laboratories​ ​Monday through Saturday ​1-2 days ​C2: Automated Liposome Lysis Assay
Reference Lab
Test Information
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. These patients have increased susceptibility to infections with encapsulated microorganisms. They may also have symptoms that suggest autoimmune disease, and complement deficiency may be an etiologic factor in the development of autoimmune disease.
 
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 (the prevalence of heterozygotes is 1 in 100 to 1 in 50). 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, atrophoderma, 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.
Reference Range Information
Performing Location Reference Range
​Mayo Labs ​25 - 47 U/mL
Interpretation
Low levels of complement may be due to inherited deficiencies, acquired deficiencies, or due to complement consumption (eg, as a consequence of infectious or autoimmune processes).
 
Absent (or low) C2 levels in the presence of normal C3 and C4 values are consistent with a C2 deficiency.
 
Low C2 levels in the presence of low C3 and C4 values are consistent with a complement-consumptive process.
 
Low C2 and C4 values, in the presence of normal values for C3 is suggestive of C1 esterase inhibitor deficiency.
Outreach CPTs
CPT Modifier
(if needed)
Quantity Description Comments
86161​ ​1
​86160 ​2 ​If needed
Synonyms/Keywords
C2 Functional
Test Components

If the C2 result is <15 U/mL, then C3 and C4 will be performed at an additional charge.

Ordering Applications
Ordering Application Description
​COM ​C2 Complement w/Reflex
If the ordering application you are looking for is not listed, contact your local laboratory for assistance.
Specimen Requirements
Fasting Required Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)
Pediatric Minimum Volume
(no repeat)
8 hour fast preferred (not required)​ ​Serum ​Red Top Tube (RTT) ​1 mL ​0.5 mL
Collection Processing Instructions
Immediately after drawing the specimen, place the tube on wet ice. Spin down and separate serum from clot. Immediately freeze serum specimen.
Specimen Stability Information
Specimen Type Temperature Time
Serum​ ​Frozen ​21 days
Rejection Criteria
Gross lipemia
Interference
As with all complement assays, proper sample handling is of utmost importance to ensure that the complement system is not activated before clinical testing.
 
Absent (or low) C2 functional levels in the presence of normal C2 antigen levels should be replicated with a new serum specimen to confirm that C2 inactivation has not occurred during shipping.
Useful For
The investigation of a patient with a low (absent) hemolytic complement (CH50), with reflex testing to C3 and C4, if appropriate.
Test Information
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. These patients have increased susceptibility to infections with encapsulated microorganisms. They may also have symptoms that suggest autoimmune disease, and complement deficiency may be an etiologic factor in the development of autoimmune disease.
 
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 (the prevalence of heterozygotes is 1 in 100 to 1 in 50). 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, atrophoderma, 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.
Reference Range Information
Performing Location Reference Range
​Mayo Labs ​25 - 47 U/mL
Interpretation
Low levels of complement may be due to inherited deficiencies, acquired deficiencies, or due to complement consumption (eg, as a consequence of infectious or autoimmune processes).
 
Absent (or low) C2 levels in the presence of normal C3 and C4 values are consistent with a C2 deficiency.
 
Low C2 levels in the presence of low C3 and C4 values are consistent with a complement-consumptive process.
 
Low C2 and C4 values, in the presence of normal values for C3 is suggestive of C1 esterase inhibitor deficiency.
For more information visit:
Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
Mayo Medical Laboratories​ ​Monday through Saturday ​1-2 days ​C2: Automated Liposome Lysis Assay
Reference Lab
For billing questions, see Contacts
Outreach CPTs
CPT Modifier
(if needed)
Quantity Description Comments
86161​ ​1
​86160 ​2 ​If needed
For most current information refer to the Marshfield Laboratory online reference manual.