C1 inhibitor is a multispecific, protease inhibitor that is present in normal human plasma and serum, and which regulates enzymes of the complement, coagulation, fibrinolytic, and kinin-forming systems. The enzymes (proteases) regulated by this protein include the C1r and C1s subunits of the activated first component of complement, activated XIIa, kallikrein (Fletcher factor), and plasmin.

Measurement of the C1 esterase inhibitor (the first component of the complement) is used to diagnose hereditary angioedema and to monitor levels of the inhibitor during treatment.

The complement system is a group of nearly 60 proteins in blood plasma or on the surface of some cells. The complement proteins work with your immune system to protect the body from infections. They also help remove dead cells and foreign material. There are nine major complement proteins. They are labeled C1 through C9.

In some rare cases people may inherit deficiency of some complement proteins. These people are prone to certain infections or autoimmune disorders.

C3 Complement, often simply referred to as C3, is a crucial protein component of the immune system's complement system. The complement system is a part of the innate immune response and plays a significant role in inflammation and defending against infections. C3, in particular, is central to the activation of the complement system. It gets activated through one of the three complement pathways (classical, lectin, or alternative) and subsequently participates in opsonization (marking pathogens for destruction), chemotaxis (attracting immune cells to the site of infection), and cell lysis (breaking down of cells).

desArg = without arginine

C3a desArg is a cleavage product of C3 complement component activation. Elevated levels of C3a have been reported in patients with acute lyme disease, acute pancreatitis, systemic lupus erythematosus, and adult respiratory distress syndrome.

C4 Complement, an essential component of the immune system's complement pathway, plays a pivotal role in both innate and adaptive immunity. Similar to C3, C4 is involved in the activation of the complement system, particularly in the classical and lectin pathways. Activation of C4 leads to its cleavage into C4a and C4b, with the latter playing a key role in opsonization (coating pathogens to promote phagocytosis) and in the formation of the C3/C5 convertase, crucial for further complement activation. Measuring the levels of C4 in the blood is an important diagnostic tool, especially in autoimmune and inflammatory conditions.

C4a Level by RIA (Radioimmunoassay) is an important test in immunology, offering insights into the body's immune response, particularly in the context of inflammation and autoimmune disorders. The C4a component is a part of the complement system, a group of proteins in the blood that play a crucial role in the body's defense against infections and in the process of inflammation. When the complement system is activated in response to a threat like an infection, C4a is produced as a byproduct. Measuring the levels of C4a, therefore, can help in understanding if the complement system is overactive, which is often the case in autoimmune diseases or during certain allergic reactions.

A CA 125 test may be used to monitor certain cancers during and after treatment. In some cases, a CA 125 test may be used to look for early signs of ovarian cancer in people with a very high risk of the disease.

Cancer antigen 15-3 (CA 15-3) is used to monitor response to breast cancer treatment and disease recurrence.

The reference range of serum CA 15-3 is less than 30 U/mL. The upper limit of the range varies depending on the laboratory and kit used for the test. Values obtained with different assay kits, methods, or laboratories cannot be used interchangeably.

CA 15-3 levels are most commonly used to monitor metastatic breast cancer during active therapy. Tumor marker levels must be used in conjunction with the history, physical examination, and diagnostic imaging. A decrease in marker levels during treatment can indicate tumor response, whereas stable or increasing levels despite adequate treatment can indicate that the tumor is not responding to treatment or that the tumor is recurring.

CA 15-3 measurement can also be used to survey disease recurrence after treatment of metastatic breast cancer. In the absence of measurable disease, an increase in CA 15-3 levels could indicate treatment failure. However, CA 15-3 levels can rise during the initial 4-6 weeks of starting therapy. This transient rise does not usually correlate with disease progression.

A CA 19-9 test measures the amount of a protein called CA 19-9 (cancer antigen 19-9) in a sample of your blood. CA 19-9 is a type of tumor marker. Tumor markers are substances made by cancer cells or by normal cells in response to cancer in your body.

Healthy people can have small amounts of CA 19-9 in their blood.