Description of the blood test:

C1-inhibitor (C1-INH) is a vital regulatory protein that controls several inflammatory pathways in the body, including the complement system and the kinin system. Its primary role is to prevent the excessive production of bradykinin, a substance that causes blood vessels to leak fluid into surrounding tissues. A deficiency or dysfunction of this protein leads to Hereditary Angioedema (HAE), a condition characterized by sudden, severe, and potentially life-threatening swelling of the skin, gastrointestinal tract, or airway.

What Does the Test Represent?

• Goal: To measure both the amount (concentration) and the functionality (activity) of the C1-inhibitor protein.
• Main Application: Diagnosing Hereditary Angioedema (Types I and II) and differentiating it from common allergies.
• Method: Nephelometry (for concentration) and Chromogenic/ELISA assays (for functional activity).

Collection Recommendations (General)

• Timing: Blood collection is best performed in the morning.
• Fasting: Overnight fasting (8–12 hours) is recommended; plain water is allowed.
• Material: Venous blood (plasma or serum).
• Specific Rules: If possible, testing should be conducted during or shortly after an edema “attack” for the most accurate diagnostic picture, though it can be done during stable periods. Avoid intense physical stress before the draw.

Factors Influencing the Result

• Factors Altering Levels: Estrogen-containing medications (like certain birth control pills) can trigger attacks or lower functional levels in susceptible individuals.
• Physical Conditions: Pregnancy can naturally alter complement protein levels.
• Sample Handling: C1-inhibitor activity is highly sensitive to temperature. The sample must be processed quickly and kept cold to avoid false-low activity results.

When to Take This Test?

• Recommendations: If you experience recurrent episodes of swelling (especially in the face, hands, or feet) that do not respond to antihistamines or steroids, or unexplained severe abdominal pain.
• Importance: Distinguishing HAE from a standard allergic reaction is life-saving, as the treatments for these conditions are entirely different.

Medical Interpretation

• Crucial Note: The interpretation of C1-inhibitor results is a specialized clinical task. A normal concentration does not always rule out disease if the protein isn’t working correctly. Only a specialist can “fine-tune” these results by correlating them with your family history and clinical symptoms.
• Low Concentration & Low Activity: Typically indicates HAE Type I (the most common form).
• Normal Concentration & Low Activity: Indicates HAE Type II (the protein is present but broken).
• Low Levels in Adulthood: May suggest Acquired Angioedema (AAE), which can be associated with other underlying immune or lymphoproliferative disorders.

Possible Further Investigations

• C4 Complement Component: Almost always low during an HAE attack; serves as an excellent screening tool.
• C1q Quantitative: Helps differentiate between Hereditary (normal C1q) and Acquired (low C1q) forms of the disease.
• Genetic Testing: To identify specific mutations in the SERPING1 gene.
• Consultation with an Allergist or Immunologist.

When Does the Next Step Make Sense?

• If a deficiency is confirmed, the next step is developing an emergency action plan and identifying specific “rescue” medications. Family screening is also highly recommended, as this is a genetic condition.
• All clinical decisions must be made by a healthcare professional based on the specific subtype of deficiency identified.

👉 If necessary, you can discuss the analysis results with a specialist such as an Immunologist (Doctors – TAMC).