see CH50 assay and CH50 unit.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

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).


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

Normal findings

(Method: Quantitative hemolysis)
Conventional UnitsSI Units (Conventional Units × 1)
25–110 CH50 units/mL25–110 CH50 kU/L


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



  • 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

    Autoimmune diseases (related to continuous demand) Autoimmune hemolytic anemia (related to consumption during hemolytic process) Burns (related to increased consumption from initiation of complement cascade) Cryoglobulinemia (related to increased consumption) Hereditary deficiency (related to insufficient production) Infections (bacterial, parasitic, viral; related to increased consumption during immune response) Liver disease (related to decreased production by damaged liver cells) Malignancy (related to consumption during cellular immune response) Membranous glomerulonephritis (related to consumption during cellular immune response) Rheumatoid arthritis (related to consumption during immune response) SLE (related to consumption during immune response) Trauma (related to consumption during immune response) Vasculitis (related to consumption during cellular immune response)

Critical findings


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


  • 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.


  • 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.


  • 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.
Handbook of Laboratory and Diagnostic Tests, © 2013 Farlex and Partners
References in periodicals archive ?
An antinuclear antibody (ANA) test was strongly positive at 1:1,280, homogenous pattern, her rheumatoid factor was elevated, and complement factors C3, C4, CH50 were all low, suggesting an autoimmune process was present.
CH50 testing is the most common assay used to screen patients for the functional activity of the classical complement pathway, and in the work up of complement deficiency.
Complement profile initially revealed normal C4 and low C3 and CH50 (C3 84.1 mg/dL, normal 90-180 mg/dL and CH50 32%, normal 70%-130%).
Serological data of enrolled patients Anti-cardiolipin CH50 C4 C3 dsDNA ANA [beta]2- Glycoprotein Mean 4.5 80 0.14 0.55 4.2 7.64 3.7 Min 0.12 3 0.01 0 0.1 0.8 0.5 Max 43 135 100 180 600 1180 25.7 ANA: antinuclear antibod Table 3.
All seven patients that completed the study had a CH50 level below the limit of quantification after the ablating dose phase indicating total blockade of the terminal complement pathway.
Immunology workup revealed low complement C3 and C4 with high CH50, high titer of antidouble stranded DNA (dsDNA) antibody, positive LA, positive aCL, and negative aB2GPI.
The alternative and classical complement pathways were suppressed confirming drug action (CH50 and AP50 hemolytic assays < 10%).
A reduction in CH50 plasma levels and increased C3 in patients with EMAP could indicate a more severe complement pathway dysfunction compared to AMD and play a role in increased pseudodrusen formation and atrophy progression [1].
Although C3 or C4 levels were also within normal range, CH50 was slightly higher (59.4 U/mL) than the normal range (32-48 U/mL).