What this test measures
Serum amyloid A (SAA) is an apolipoprotein produced by the liver in response to inflammatory cytokines (IL-1, IL-6, TNF-α). Like CRP it is an acute-phase reactant — but SAA rises faster and to a greater magnitude (up to 1000-fold within 24 hours of an inflammatory trigger), making it a very sensitive marker of inflammation. Levels normally fall just as rapidly once inflammation resolves.
Persistently elevated SAA over months to years leads to deposition of misfolded SAA fragments as AA-amyloid in kidneys, liver, and gut — secondary amyloidosis. This is a complication of long-standing inflammatory disease (rheumatoid arthritis, ankylosing spondylitis, chronic infections, familial Mediterranean fever, IBD).
Why it matters
SAA testing has three main clinical uses. First, sensitive monitoring of inflammatory disease activity — rheumatoid arthritis, juvenile idiopathic arthritis, vasculitis, IBD — where SAA may detect smouldering inflammation that CRP misses. Second, AA-amyloidosis risk in patients with chronic inflammatory disease; persistently raised SAA increases risk of renal amyloid deposition. Third, in familial Mediterranean fever — SAA is used to confirm adequate colchicine therapy (target SAA < 10 mg/L) to prevent renal amyloidosis.
In India, SAA is less widely available than CRP but is increasingly ordered by rheumatologists in difficult-to-control inflammatory arthritis and in familial periodic fever syndromes. It is also a research marker of cardiovascular inflammation similar to hs-CRP.
How to prepare
No fasting required. Continue all medications. Disclose any active infection or inflammation (which raises SAA acutely) and any chronic inflammatory disease being monitored.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| Serum Amyloid A (mg/L)[1][2][3] | < 6.4 mg/L (healthy adult; assay-specific) | < 6.4 mg/L: no significant active inflammation. In a patient with chronic inflammatory disease, a normal SAA supports good disease control. | 6.4 – 50 mg/L: mild to moderate inflammation. 50 – 500 mg/L: moderate to severe inflammation — active autoimmune flare, infection, post-surgical state. > 500 mg/L: severe inflammation — sepsis, severe autoimmune flare, major trauma. Persistent elevation > 6 months in inflammatory disease increases AA-amyloidosis risk. |
SAA vs CRP — how they compare
| Feature | SAA | CRP |
|---|---|---|
| Magnitude of rise | 100 – 1000 fold | 10 – 100 fold |
| Onset | 6 – 12 h | 6 – 12 h |
| Peak | 24 – 48 h | 24 – 48 h |
| Sensitivity in low-grade inflammation | Higher | Moderate |
| Cost and availability | More expensive, less widely available | Cheap, widely available |
| Cardiovascular risk | Research marker | hs-CRP is established |
| AA-amyloidosis risk monitoring | Standard | Less specific |
Frequently asked questions
When is SAA preferred over CRP?
When highly sensitive detection of low-grade inflammation is needed — for example, monitoring familial Mediterranean fever to prevent amyloid deposition, or tracking residual disease activity in well-controlled rheumatoid arthritis where CRP may be normal but inflammation is still smouldering.
How is SAA used in familial Mediterranean fever?
Colchicine prophylaxis aims to keep SAA below 10 mg/L between attacks. Persistent SAA elevation despite colchicine indicates inadequate disease control and increases the risk of renal AA-amyloidosis — an indication to escalate to biologics (IL-1 inhibitors).
What is AA-amyloidosis?
A secondary amyloidosis where SAA fragments deposit as amyloid fibrils in kidneys (causing nephrotic syndrome), liver, gut, and spleen. It complicates chronic inflammatory diseases — RA, ankylosing spondylitis, IBD, FMF, chronic infection. Risk is proportional to duration and magnitude of SAA elevation.
Is SAA useful in cardiovascular risk?
Research suggests it has some role similar to hs-CRP, but it is not yet a routine cardiovascular risk marker. hs-CRP remains the standard for cardiovascular risk assessment.
How long does SAA take to fall?
SAA falls quickly once inflammation resolves — within 24–48 hours of effective treatment. This makes it a useful real-time marker of treatment response, similar to CRP but more sensitive at the lower end.
Should I worry about a slightly raised SAA?
Mild persistent elevation may reflect chronic low-grade inflammation (obesity, smoking, periodontitis, undiagnosed autoimmune disease). Persistent elevation over months in someone with chronic inflammatory disease warrants discussion about disease control and amyloidosis risk.
Do I need to fast?
No fasting required.
Related Immunology tests
Tests commonly ordered alongside SERUM AMYLOID A PROTEIN, or that help interpret an unexpected result.
Sources & references
- NCBI StatPearls — Acute Phase Reactants · accessed 2026-05-30T00:00:00.000Z
- Mayo Clinic Labs — Serum Amyloid A · accessed 2026-05-30T00:00:00.000Z
- NIH PMC — SAA in cardiovascular and inflammatory disease · accessed 2026-05-30T00:00:00.000Z
- International Society of Amyloidosis · accessed 2026-05-30T00:00:00.000Z
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