Complement, Total

Synonym/acronym: Total hemolytic complement, CH₅₀, CH₁₀₀.

Common use

To evaluate immune diseases related to complement activity and follow up on a patient’s response to therapy such as treatment for systemic lupus erythematosus (SLE).

Specimen

Serum (1 mL) collected in a red-top tube.

Normal findings

(Method: Quantitative hemolysis)

Conventional Units	SI Units (Conventional Units × 1)
25–110 CH₅₀ units/mL	25–110 CH₅₀ kU/L

Description

The complement system comprises proteins that become activated and interact in a sequential cascade. The complement system is an important part of the body’s natural defense against allergic and immune reactions. It is activated by plasmin and is interrelated with the coagulation and fibrinolytic systems. Activation of the complement system results in cell lysis, release of histamine, chemotaxis of white blood cells, increased vascular permeability, and contraction of smooth muscle. The activation of this system can sometimes occur with uncontrolled self-destructive effects on the body. In the serum complement assay, a patient’s serum is mixed with sheep red blood cells coated with antibodies. If complement is present in sufficient quantities, 50% of the red blood cells are lysed. Lower amounts of lysed cells are associated with decreased complement levels.

This procedure is contraindicated for

N/A

Indications

Assist in the diagnosis of hereditary angioedema
Evaluate complement activity in autoimmune disorders
Evaluate and monitor therapy for systemic lupus erythematosus (SLE)
Screen for complement deficiency

Potential diagnosis

Increased in

Acute-phase immune response (related to sudden response to increased demand)

Decreased in

(related to continuous demand)

(related to consumption during hemolytic process)

(related to increased consumption from initiation of complement cascade)

(related to increased consumption)

(related to insufficient production)

(bacterial, parasitic, viral; related to increased consumption during immune response)

(related to decreased production by damaged liver cells)

(related to consumption during cellular immune response)

(related to consumption during immune response)

(related to consumption during cellular immune response)

Critical findings

N/A

Interfering factors

Drugs that may increase total complement levels include cyclophosphamide and oral contraceptives.
Specimen should not remain at room temperature longer than 1 hr.

Nursing Implications and Procedure

Pretest

Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
Patient Teaching: Inform the patient this test can assist in evaluating response to treatment for infection or disease.
Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
Obtain a history of the patient’s immune system and results of previously performed laboratory tests and diagnostic and surgical procedures.
Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values).
Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
Note that there are no food, fluid, or medication restrictions unless by medical direction.

Intratest

Potential complications: N/A
Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
Promptly transport the specimen to the laboratory for processing and analysis.

Post-Test

Inform the patient that a report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

Related tests include antibody anticytoplasmic neutrophilic, ANA, Coombs’ antiglobulin, complement C3 and C4, cryoglobulin, ESR, G6PD, Ham’s test, osmotic fragility, PK, and RF.
Refer to the Immune System table at the end of the book for related tests by body system.