Complement, Total (CH50)

The Complement, Total (CH50) test contains 1 test with 1 biomarker.

Brief Description: The Complement Total (CH50) test is a blood test that measures the overall activity of the complement system, a group of proteins in the blood that play a crucial role in the immune response. The test assesses the ability of the complement system to destroy foreign particles, such as bacteria and immune complexes.

Also Known As: CH50 Test, Total Complement Test, Complement Activity Test, Total Complement Activity Test

Collection Method: Blood Draw

Specimen Type: Serum

Test Preparation: No preparation required

When is a Complement Total test ordered?

When a person exhibits inexplicable edema, inflammation, or indications of an autoimmune condition like SLE, complement testing may be mandated. It may also be requested when a medical professional wants to assess the complement system of a patient who they suspect may have an immune complex-related disease.

When the total complement activity is abnormal, individual complement components may be ordered to help identify which ones are lacking or defective.

Complement testing may be used to provide a general assessment of the severity of an acute or chronic ailment after a diagnosis, with the underlying supposition that the severity is related to the decline in complement levels. Occasionally, a doctor may also request complement testing to keep track of the progression of a problem.

What does a Complement Total blood test check for?

Over 30 blood proteins make up the intricate complement system, which functions to support inflammatory and immunological responses. Its main function is to eliminate invading infections like viruses and bacteria. The body's production of antibodies against its own tissues, which occurs in autoimmune disorders, can also cause the complement system to become active. The amount or activity of complement proteins in the blood is measured by complement assays.

A component of the body's innate immune system is the complement system. The innate immune system is non-specific and rapid to react to external molecules, in contrast to the acquired immune system, which generates antibodies that target and defend against specific threats. It does not require prior exposure to an invasive drug or bacterium and does not keep track of prior interactions.

The primary complement proteins are numbered C1 through C9. There are nine of them. Together with the remaining proteins, these elements produce complexes that react to infections, non-self tissues, dead cells, or inflammation by activating, amplifying, breaking apart, and generating complexes.

Lab tests often ordered with a Complement Total test:

When a CH50 test is ordered, it's often part of a broader evaluation for autoimmune diseases, recurrent infections, or unexplained inflammation. Here are some tests commonly ordered alongside it:

1. Complement Components C3 and C4:

   • Purpose: To measure levels of C3 and C4, individual components of the complement system.
   • Why Is It Ordered: To identify deficiencies or abnormalities in specific complement components, which can be associated with certain autoimmune and inflammatory disorders.

2. Antinuclear Antibodies (ANA) Test:

   • Purpose: To screen for antibodies that target nuclear components of cells, common in autoimmune diseases.
   • Why Is It Ordered: To indicate the presence of autoimmune disorders such as systemic lupus erythematosus (SLE), where complement levels might be consumed.

3. Anti-dsDNA (Double-Stranded DNA) Antibodies:

   • Purpose: To detect antibodies against double-stranded DNA.
   • Why Is It Ordered: These antibodies are specific for SLE, a condition that can cause decreased complement levels.

4. Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP):

   • Purpose: To measure markers of inflammation.
   • Why Is It Ordered: To assess the level of inflammation, which can be associated with conditions involving complement abnormalities.

5. Rheumatoid Factor (RF) and Anti-CCP (Cyclic Citrullinated Peptide) Antibodies:

   • Purpose: To test for markers associated with rheumatoid arthritis.
   • Why Is It Ordered: To differentiate between various autoimmune diseases, as some can affect complement levels.

6. Kidney Function Test:

   • Purpose: To evaluate kidney function.
   • Why Is It Ordered: Because the kidneys can be affected in diseases with complement abnormalities, such as SLE and other forms of glomerulonephritis.

7. Complete Blood Count (CBC):

   • Purpose: To evaluate overall blood health.
   • Why Is It Ordered: To assess for signs of anemia or other blood cell abnormalities that can occur in autoimmune diseases.

8. Liver Function Test:

   • Purpose: To assess liver health.
   • Why Is It Ordered: As the liver produces many of the complement proteins, liver disorders can impact complement levels.

These tests, when ordered alongside a Complement Total CH50 test, provide a comprehensive assessment of the immune system and can help in diagnosing and managing autoimmune diseases, recurrent infections, and other conditions related to the complement system. The specific combination of tests will depend on the individual’s symptoms, medical history, and clinical presentation.

Conditions where a Complement Total test is recommended:

• Complement Deficiencies: Deficiencies in complement components can lead to increased susceptibility to infections and certain autoimmune disorders.
• Autoimmune Disorders: Conditions like systemic lupus erythematosus (SLE), rheumatoid arthritis, and immune complex diseases can involve complement system dysfunction.
• Kidney Diseases: Certain kidney diseases, like lupus nephritis, might show abnormal complement activity.

How does my health care provider use a Complement Total test?

When a person has a disease or illness, complement tests are done to evaluate whether deficiencies or abnormalities in the complement system are the root cause or a contributing factor. In order to assess the overall integrity of the classical complement pathway, total complement activity may be ordered. To check for deficits, additional complement components are obtained if necessary.

What do my Complement Total test results mean?

It's possible for complement levels to drop as a result of greater intake or, less frequently, a congenital deficiency. A high incidence of recurrent microbial infections is typically caused by a hereditary defect in one of the complement proteins. Reduced complement levels are linked to a higher risk of autoimmune disease development.

Complement levels will typically return to normal if the underlying acute or chronic ailment can be treated if the deficiency is brought on by one of these.

During acute or chronic inflammation, complement protein levels typically rise together with those of other unrelated proteins known as acute phase reactants. When the underlying illness is treated, all of these often return to normal. Comparatively to the frequently ordered C-reactive protein (CRP), complement proteins are less frequently assessed in these circumstances; hence, the value of their testing in these circumstances is not discussed here.

Most Common Questions About the Complement Total (CH50) test:

Clinical Utility and Interpretation

What is the Complement Total (CH50) test, and why is it performed?

The Complement Total (CH50) test measures the activity of the classical complement pathway, a series of proteins involved in immune response. The test is often used to diagnose or monitor immune system disorders, including autoimmune diseases like lupus, and certain infections or kidney diseases.

How are the results of the Complement Total (CH50) test interpreted?

The results of the Complement Total (CH50) test are usually expressed as a numerical value. A normal result indicates that the complement system is functioning properly. A low CH50 value may indicate a deficiency in one or more complement proteins, while a high value might suggest an active inflammatory process or infection.

Clinical Applications and Diagnoses

When is the Complement Total (CH50) test typically ordered?

The Complement Total (CH50) test is often ordered when a patient exhibits symptoms of an autoimmune disorder, or if there's a suspicion of a complement system deficiency. It may also be used to monitor the activity of diseases like lupus.

Can the Complement Total (CH50) test differentiate between complement pathway deficiencies?

The Complement Total (CH50) test mainly evaluates the classical pathway, and a low result may indicate a deficiency in one of the components. Specific complement component tests (e.g., C3, C4) may be ordered to identify which part of the pathway is affected.

Comparative Insights

How does the Complement Total (CH50) test compare to other tests assessing the complement system?

The Complement Total (CH50) test is a general assessment of the classical pathway. In contrast, individual component tests can provide more detailed insights into specific deficiencies or abnormalities. The combination of CH50 with other specific tests provides a comprehensive analysis of the complement system.

Understanding Limitations and Challenges

What are some of the limitations of the Complement Total (CH50) test?

The Complement Total (CH50) test mainly evaluates the classical pathway, so it might not detect deficiencies or abnormalities in the alternative or lectin pathways. Additionally, transient changes in complement levels due to infections or other factors might affect the results.

How might recent illnesses or treatments affect the Complement Total (CH50) test results?

Recent infections, inflammation, or treatments with certain medications like corticosteroids might temporarily alter complement levels. These factors can affect the Complement Total (CH50) test results and should be considered when interpreting the findings.

Additional Questions and Insights

What role does the Complement Total (CH50) test play in monitoring treatment for autoimmune diseases?

The Complement Total (CH50) test can be used to monitor treatment responses in autoimmune diseases like lupus. Changes in CH50 levels might reflect changes in disease activity, and serial testing can help guide treatment decisions.

Can the Complement Total (CH50) test be used to detect infections?

While the Complement Total (CH50) test is not specific for infections, an elevated CH50 level might indicate an ongoing infection or inflammatory process. Additional tests are typically required to identify the underlying cause.

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.