Advanced Diagnostic Laboratories

Classical Complement Pathway Activity (CH50)

Test Code

CM50

Description

The complement system is part of our innate immune response. It is vital to our defense against invasive microorganisms. Complement activation can occur through the classical, lectin and alternative pathway, which then converge to a common terminal pathway. Activation of the complement pathway(s) results in the generation of biologically active peptides, also known as complement split products, and referred to as anaphylatoxins (C4a, C3a, C5a) which protect us from invasive microorganisms by enhancing inflammation, facilitating the clearance of immune complexes and apoptotic cells, enhancing cellular, and antibody immune responses, and altering vascular permeability, as well as smooth muscle contractility.

Complement deficiency can lead to life-threatening infections well as long-term autoimmune conditions such as systemic lupus erythematosus (SLE) and hereditary angioedema (HAE). The CH50 hemolytic assay is a sensitive method for detection of total classical complement activity or lack thereof. Severe or recurrent infections that produce strong activation of the classical complement pathway may lower CH50 levels below normal. Genetic or acquired complement deficiency involving the classical complement pathway components (C1q, C1r, C1s, C2, C4, and C3) as well as terminal complement components (C5, C6, C7, C8, and C9) may also lower CH50 levels. The CH50 assay can also be utilized to monitor response to anti-complement therapies.

Collect

Serum from a red top tube is the only acceptable sample type. Mix sample thoroughly. Keep tubes cold on wet ice or with a cold pack after collection. Gel barrier tubes are not acceptable.

Patient Prep

Within 30 minutes of venipuncture, centrifuge the collection tube at 1600 (±200) x g (rcf) at 4°C (± 2°C) for 15 (± 1) minutes. Transfer the cell-free serum to a clean tube and immediately store samples at –60°C or below in an ultra-low freezer.

Preferred volume: 1 mL

Ambient temperature for centrifugation is acceptable provided that the time between collection and storage is minimized (approximately 30 minutes).

Pediatric Collection

Minimum volume: 0.25 mL serum, frozen

Unacceptable Conditions

Thawed specimen or specimens stored at room temperature prior to shipment

Storage Transport Temp

Send frozen serum Priority Overnight via FedEx and in a well insulated container on dry ice.

Stability

-60°C or below in an ultra-low freezer - up to 2 years

Notes

Additional testing time may be needed for less than perfect samples or confirmatory/reflex testing.

Performed

Monday - Friday

Methodology

Hemolytic Assay

Turnaround Time

Up to 4 weeks

Department

Complement Lab

Synonyms

Hemolytic Assay (Classical Complement Pathway Activity), Classical Complement Pathway Activity, Complement (Classical Complement Pathway Activity), CM50

Study Offerings

CAP/CLIA

Related Tests

Primary Immunodeficiency Screen: Pneumococcal polysaccharide IgG antibody [12 serotypes] (PNU12), Diphtheria IgG antibody titer (DIPHT), Tetanus IgG antibody titer (TET), Lymphocyte enumeration, CDC panel [CD3/CD4, CD3/CD8, CD19, CD16/56] (TBCDC), CBC with automated diff (HCBC), Immunoglobulin A level (IGA), Immunoglobulin G level (IGG), Immunoglobulin M level (IGM), Alternative complement pathway activity (AH50)
Complement Assessment: Alternative complement pathway activity (AH50), Mannose binding lectin [MBL] level (MLEC)

Reference Interval

176-382

Interpretation

Low CH50 level is indicative of a reduction, absence, and/or inactivity of any components of the classical complement pathway and/or terminal complement pathway. Anti-complement therapy with C5 inhibitors including Eculizumab or Ravulizumab is associated with complete loss or reduced CH50 level.