Synonym/Acronym
Total hemolytic complement, CH50, CH100.
Rationale
To detect inborn complement deficiency, evaluate immune diseases related to complement activity, and follow up on a patient’s response to therapy such as treatment for rheumatoid arthritis and systemic lupus erythematosus (SLE) in which complement is consumed at an increased rate.
Patient Preparation
There are no food, fluid, activity, or medication restrictions unless by medical direction.
Normal Findings
Method: Immunoturbidimetric for C3 and C4.
Total Complement (CH50)
| Complement Total (CH50) Units/mL | Method |
|---|
| 39–90 | Immunoturbidimetry | | 23–60 | Liposome Immunoassay | | 60–140 | Enzyme Immunoassay | | 100–300 | Quantitative Hemolysis (Classical method) |
|
C3
| Age | Conventional Units | SI Units (Conventional Units × 0.01) |
|---|
| Newborn | 57–116 mg/dL | 0.57–1.16 g/L | | 6 mo–adult | 74–166 mg/dL | 0.74–1.66 g/L | | Adult | 83–200 mg/dL | 0.83–2 g/L |
|
C4
| Age | Conventional Units | SI Units (Conventional Units × 0.01) |
|---|
| Newborn | 10–31 mg/dL | 0.1–0.31 g/L | | 6 mo–6 yr | 15–52 mg/dL | 0.15–0.52 g/L | | 7–12 yr | 19–40 mg/dL | 0.19–0.4 g/L | | 13–15 yr | 19–57 mg/dL | 0.19–0.57 g/L | | 16–18 yr | 19–42 mg/dL | 0.19–0.42 g/L | | Adult | 12–36 mg/dL | 0.12–0.36 g/L |
|
Study type: Blood collected in a red-top tube; related body system: Immune system.
Complement is a system of 25 to 30 distinct cell membrane and plasma proteins, numbered C1 through C9. It 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. Once activated, the proteins interact with each other in a specific sequence called the complement cascade.
The classical pathway is triggered by antigen-antibody complexes and includes participation of all complement proteins C1 through C9. The alternate pathway occurs when C3, C5, and C9 are activated without participation of C1, C2, and C4 or the presence of antigen-antibody complexes. 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, therefore, serum complement levels are also used to detect autoimmune diseases.
C3 and C4 are the most frequently assayed complement proteins, along with total complement. Circulating C3 is synthesized in the liver and comprises 70% of the complement system, but cells in other tissues can also produce C3. C3 is an essential activating protein in the classic and alternate complement cascades. It is decreased in patients with immunological diseases, in whom it is consumed at an increased rate. C4 is produced primarily in the liver but can also be produced by monocytes, fibroblasts, and macrophages. C4 participates in the classic complement pathway.
Factors That May Alter the Results of the Study
- Drugs that may increase total complement levels include cyclophosphamide and oral contraceptives.
- Drugs and other substances that may increase C3 levels include cimetidine and cyclophosphamide.
- Drugs and other substances that may decrease C3 levels include danazol, methyldopa, and phenytoin.
- Drugs and other substances that may increase C4 levels include cimetidine, cyclophosphamide, and danazol.
- Drugs and other substances that may decrease C4 levels include dextran and penicillamine.
Other Considerations
- Specimen should not remain at room temperature longer than 1 hr.
| Normal C4 and decreased C3 | Acute glomerulonephritis, membranous glomerulonephritis, immune complex diseases, SLE, C3 deficiency | | Decreased C4 and normal C3 | Immune complex diseases, cryoglobulinemia, C4 deficiency, hereditary angioedema | | Decreased C4 and decreased C3 | Immune complex diseases |
|
Increased In
Total Complement, C3 and C4
- Acute-phase immune response (related to sudden response to increased demand)
C3
C4
Decreased In
Total Complement
- 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)
Total Complement, C3 and C4
Related to Overconsumption During Immune Response
- Hereditary deficiency (insufficient production)
- Liver disease (insufficient production related to damaged liver cells)
- SLE
C3
C4
Before the Study: Planning and Implementation
Teaching the Patient What to Expect
- Discuss how this test can assist in diagnosing diseases of the immune system and evaluating response to treatment for infection or disease.
- Explain that a blood sample is needed for the test.
After the Study: Implementation & Evaluation Potential Nursing Actions
Treatment Considerations
- Review test results in relation to the patient’s symptoms and other tests performed and potential changes in the plan of care.
Clinical Judgement
- Consider how to address lifestyle changes necessary to conform to mobility changes related to the disease process.
Follow-Up and Desired Outcomes
- Understands that the cause of immune system disease may be genetic influences.
- Agrees to participate in recommended therapeutic treatments that support independent functioning and enhance quality of life.