SAA (Serum Amyloid A)
Overview
Serum amyloid A (SAA) measures circulating levels of this acute-phase protein primarily produced by hepatocytes in response to interleukin-6 and other cytokines during inflammation. It functions as an opsonin, participates in cholesterol transport during inflammation, and modulates immune responses. Elevated SAA levels indicate acute or chronic inflammation, infection, trauma, or tissue damage, while low levels suggest absence of significant inflammatory activity; it is clinically useful as a sensitive, non-specific marker outperforming CRP in some infections and for monitoring inflammatory disease activity when combined with other biomarkers.
Clinical Use Cases
- Monitoring infection severity and response to antibiotic therapy.
- Assessing inflammation in rheumatoid arthritis and other autoimmune diseases.
- Evaluating cardiovascular risk in inflammatory conditions.
- Diagnosing and monitoring amyloidosis (AA type).
- Differentiating bacterial from viral infections in research settings.
Specimen Types
- Serum.
- Plasma (EDTA or heparin).
Measurement Methods
- Immunoturbidimetric assay.
- Enzyme-linked immunosorbent assay (ELISA).
- Nephelometry.
- Automated clinical chemistry analyzers.
Test Preparation and Influencing Factors
- No fasting required.
- Acute inflammation, infection, surgery, or trauma rapidly elevate levels.
- Levels rise within 6-12 hours of inflammatory stimulus.
- Corticosteroids and anti-inflammatory drugs decrease SAA.
- Genetic polymorphisms affect baseline levels.
Synonyms
- Serum amyloid A protein.
- SAA1/SAA2 (acute-phase isoforms).