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–17 yr | 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: .)
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.
Other Considerations
| 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
C3
C4
Decreased In
Total Complement
Total Complement, C3 and C4
Related to Overconsumption During Immune Response
C3
C4
Before the Study: Planning and Implementation
Teaching the Patient What to Expect
After the Study: Implementation & Evaluation Potential Nursing Actions
Treatment Considerations
Clinical Judgement
Follow-Up Evaluation and Desired Outcomes