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Test Code C5AG C5 Complement, Antigen, Serum

Performing Laboratory

Mayo Medical Laboratories in Rochester

Reporting Name

C5 Complement, Antigen, S

Specimen Type

Serum


Specimen Required


Collection Container/Tube:

Preferred: Red top

Acceptable: Serum gel

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions:

1. Fasting

2. Spin down and separate serum from clot.


Reject Due To

Hemolysis

Mild OK; Gross OK

Lipemia

Mild OK; Gross reject

Icterus

Mild OK; Gross OK

Other

NA

Specimen Stability Information

Specimen Type Temperature Time
Serum Frozen (preferred) 60 days
  Ambient  7 days
  Refrigerated  7 days

Specimen Minimum Volume

0.5 mL

Day(s) and Time(s) Performed

Monday through Saturday; Continuous with a 3 p.m. cutoff

Specimen Retention Time

7 days

Analytic Time

Same day/1 day

Reference Values

10.6-26.3 mg/dL

Useful For

Diagnosis of C5 deficiency

 

Investigation of a patient with an absent total complement (CH50) level

Method Name

Nephelometry

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

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:1) the classic pathway, 2) the alternative (or properdin) pathway, and 3) 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).

  

The absence of early components (C1-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 clear immune complexes or to generate lytic activity. 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.  

 

More than 30 cases of C5 deficiency have been reported. Most of these patients have neisserial infections.

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 C5 levels in the presence of normal C3 and C4 values are consistent with a C5 deficiency. Absent C5 levels in the presence of low C3 and C4 values suggests complement consumption.

 

A small number of cases have been described in which the complement protein is present but is non functional. These rare cases require a functional assay to detect the deficiency C5FX / C5 Complement, Functional, Serum).

Cautions

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.

Clinical Reference

1. Sonntag J, Brandenburg U, Polzehl D, et al: Complement systems in healthy term newborns: reference values in umbilical cord blood. Pediatr Dev Pathol 1998;1:131-135

2. Prellner K, Sjoholm AG, Truedsson L: Concentrations of C1q, factor B, factor D and properdin in healthy children, and the age-related presence of circulating C1r-C1s complexes. Acta Peidiatr Scand 1987;76:939-943

3. Davis ML, Austin C, Messmer BL, et al: IFCC-standardization pediatric reference intervals for 10 serum proteins using the Beckman Array 360 system. Clin Biochem 1996;29,5:489-492

4. Gaither TA, Frank MM: Complement. In Clinical Diagnosis and Management by Laboratory Methods. 17th edition. Edited by JB Henry. Philadelphia, WB Saunders Company, 1984, pp 879-892

5. O'Neil KM: Complement defiency. Clin Rev Allergy Immunol 2000;19:83-108

6. Frank MM: Complement deficiencies. Pediatr Clin North Am 2000;47(6):1339-1354

Method Description

C5 complement antigen is measured by immunonephelometry. Antiserum to C5 is mixed with patient serum, the light scatter resulting from the antibody interaction with C5 is measured, and the signal is compared to standard concentrations of C5.(Unpublished Mayo information; Siemens Nephelometer II Operator’s Instruction Manual Version 2, 1999)