1. Introduction to Complement Factor 4 (C4)

What is Complement Factor 4 (C4)? Complement Factor 4 (C4) is a crucial protein in the complement system, a part of the immune system that enhances pathogen clearance and immune response. C4 is primarily produced by the liver and is involved in the classical and lectin complement pathways, aiding in opsonization, inflammation, and immune complex clearance. Measuring C4 levels in the blood helps diagnose autoimmune diseases, complement deficiencies, and chronic infections, and assess immune system function.

2. What is a Complement Factor 4 Unit Converter?

Definition: The Complement Factor 4 Unit Converter converts C4 concentrations between various units, enabling standardization of laboratory results for clinical use.

Purpose: It assists clinicians and researchers in interpreting C4 levels across different measurement units (e.g., µmol/L to g/L), ensuring accurate diagnosis and monitoring of immune-related disorders.

3. Importance of Complement Factor 4 Unit Conversions

Converting C4 concentrations between units is critical for:

• Standardizing Results: Different labs report C4 in various units (e.g., g/L, mg/dL); conversion ensures consistency for diagnosis.
• Clinical Diagnosis: Accurate conversions aid in diagnosing autoimmune diseases (e.g., systemic lupus erythematosus), complement deficiencies, and monitoring disease activity in chronic conditions.
• Research and Collaboration: Enables comparison of C4 data across studies or institutions using different measurement standards.

4. Clinical Significance

Elevated Levels: High C4 levels may indicate acute inflammation, infections, or chronic inflammatory conditions, as C4 can act as an acute-phase reactant. Elevated levels are less common but may occur in certain cancers or tissue injury.

Low Levels: Low C4 levels are associated with autoimmune diseases (e.g., systemic lupus erythematosus, rheumatoid arthritis), hereditary angioedema, complement deficiencies, or severe infections. Low C4 is often seen in conditions with immune complex formation or complement consumption.

Normal Ranges:

• Serum: Typically 0.1–0.4 g/L (10–40 mg/dL).
• Values vary by lab, age, and sex—consult a healthcare provider for interpretation.

5. Precautions

Interferences:

• Inflammation, infections, or medications (e.g., corticosteroids) can affect C4 levels.
• C4 should be interpreted alongside other complement components (e.g., C3) and clinical findings for accurate diagnosis.
• Sample handling (e.g., avoiding hemolysis, timely processing) is critical for reliable results—consult a healthcare provider for accuracy.

6. Frequently Asked Questions (FAQ)

Q: Why are there different units for C4?
A: Different units reflect varying standards; µmol/L and g/L are used in clinical practice, while mg/dL and mg/mL are common in some labs for consistency with other protein measurements.

Q: What is a normal C4 level?
A: Normal serum C4 is typically 0.1–0.4 g/L (10–40 mg/dL). Consult a healthcare provider for interpretation.

Q: Can this converter be used for other complement factors?
A: No, this converter is specific to C4; other complement factors (e.g., C3) have different molecular characteristics and conversion factors—consult a healthcare provider for accuracy.