Sign in →

Test Code LABC8FX C8 Complement, Functional, Serum

Additional Codes

Test Name in EPIC EPIC Test Code Mnemonic MAYO Test ID
C8 COMPLEMENT, FUNCTIONAL LABC8FX C8FX C8CF

 

Reporting Name

C8 Complement, Functional, S

Useful For

Diagnosis of C8 deficiency

 

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

Method Name

Automated Liposome Lysis Assay

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Serum Red


Advisory Information


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.



Specimen Required


Patient Preparation: Fasting preferred

Supplies: Aliquot Tube, 5 mL (T465)

Collection Container/Tube: Red top

Submission Container/Tube: Plastic, 5 mL tube

Specimen Volume: 1 mL

Collection Instructions:

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

2. Centrifuge and separate serum from clot.

3. Immediately freeze specimen.


Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Red Frozen 14 days

Reject Due To

Gross hemolysis OK
Gross lipemia Reject
Gross icterus OK

Reference Values

33-58 U/mL

Day(s) and Time(s) Performed

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

CPT Code Information

86161

LOINC Code Information

Test ID Test Order Name Order LOINC Value
C8FX C8 Complement, Functional, S 50997-6

 

Result ID Test Result Name Result LOINC Value
C8FX C8 Complement, Functional, S 50997-6

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.

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). 

 

Patients with deficiencies of the late complement proteins (C5, C6, C7, C8, and C9) are unable to form the MAC, and may have increased susceptibility to neisserial infections.

 

Most patients with C8 deficiency have invasive neisserial infections.

 

For most of the complement proteins, a small number of cases have been described in which the protein is present but is nonfunctional. 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 C8 levels in the presence of normal C3 and C4 values are consistent with a C8 deficiency. Absent C8 levels in the presence of low C3 and C4 values suggests complement consumption.

 

Normal results indicate both normal C8 protein levels and normal functional activity.

Cautions

Absent (or low) C8 functional levels in the presence of normal C8 antigen levels should be replicated with a new serum specimen to confirm that C8 inactivation did not occur during shipping.

Method Description

C8 complement activity is measured by mixing patient serum with a C8-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 C8. The target liposomes are a commercial reagent (WAKO total complement CH50), and the assay is performed on a Advia XPT.(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)

Analytic Time

Same day/1 day

Specimen Retention Time

14 days