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Test Code C3FX C3 Complement, Functional, Serum

Performing Laboratory

Mayo Medical Laboratories in Rochester

Reporting Name

C3 Complement, Functional, S

Specimen Type

Serum Red


Specimen Required


Collection Container/Tube: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions:

1. Immediately after drawing the specimen, place the tube on wet ice.

2. Spin down and separate serum from clot.

3. Immediately freeze specimen.

Additional Information: Fasting preferred.


Reject Due To

Hemolysis

Mild OK; Gross OK

Lipemia

Mild OK; Gross reject

Icterus

Mild OK; Gross OK

Other

Serum gel tube

Specimen Stability Information

Specimen Type Temperature Time
Serum Red Frozen 14 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

14 days

Analytic Time

Same day/1 day

Reference Values

21-50 U/mL

Useful For

Diagnosis of C3 deficiency

 

Investigation of a patient with undetectable total complement (CH50) level

Method Name

Automated Liposome Lysis Assay

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

86161

LOINC Code Information

Test ID Test Order Name Order LOINC Value
C3FX C3 Complement, Functional, S 87723-3

 

Result ID Test Result Name Result LOINC Value
C3FX C3 Complement, Functional, S 87723-3

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.

 

C3 is at the entry point for all 3 activation pathways to activate the MAC. C3 deficiency may result in pneumococcal and neisserial infections as well as autoimmune diseases such as glomerulonephritis.

 

Complement levels can be detected by antigen assays that quantitate the amount of the protein (C3 / Complement C3, Serum). For most of the complement proteins, a small number of cases have been described in which the protein is present but is non functional. These rare cases require a functional assay to detect the deficiency.

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 C3 levels in the presence of other normal complement values are consistent with a C3 deficiency.

Cautions

The total complement (CH50) 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.

 

Absent (or low) C3 functional levels in the presence of normal C3 antigen levels should be replicated with a new serum specimen to confirm that C3 inactivation did not occur during shipping.

Clinical Reference

1. 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

2. 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

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

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

Method Description

C3 complement activity is measured by mixing patient serum with a C3-deficient serum. The lytic activity of the serum mixture is tested against sensitized, labeled liposomes. If lysis occurs, the patient serum must be the source of the C3. The target liposomes are a commercial reagent (WAKO total complement [CH50]), and the assay is performed on a Hitachi 912.(Unpublished Mayo information Yamamoto S, Kubotsu K, Masaaki K, et al: Automated homogeneous liposome-based assay system for total complement activity. Clin Chem 1995;41:586-590)