Acute-Phase Proteins: The Evidence for CRP and SAA¶
CRP and SAA are the two acute-phase proteins that transformed inflammation testing in small-animal practice. This page summarizes the evidence behind them.
What Are Acute-Phase Proteins?¶
Acute-phase proteins are produced by the liver in response to inflammatory cytokines. Their concentration changes within hours of an inflammatory stimulus — far faster than clinical signs or leukogram changes.
| Protein | Species | Baseline | Peak | Rise time |
|---|---|---|---|---|
| CRP | Canine | < 10 mg/L | 100s of mg/L | 4–24 h |
| SAA | Feline | < 5 µg/mL | 100s of µg/mL | 3–6 h |
Species Specificity¶
The dominant acute-phase protein differs by species:
- Dog → CRP — the major canine acute-phase protein.
- Cat → SAA — the major feline acute-phase protein (rises faster and higher than canine CRP).
This is why the assays are not interchangeable — using the wrong species' marker reduces sensitivity.
The Evidence¶
The clinical utility of these markers is established:
- Inflammation detection — CRP/SAA distinguish inflammatory from non-inflammatory disease.
- Treatment monitoring — serial measurement tracks antibiotic/therapy response; a falling value confirms efficacy before clinical signs improve.
- Prognosis — persistent elevation signals ongoing disease or treatment failure.
References¶
- Nakamura M, Takahashi M, Ohno K, et al. C-reactive protein concentration in dogs with various diseases. J Vet Med Sci. 2008;70(2):127-131. PMID: 18319571
- Kajikawa T, Furuta A, Onishi T, et al. Changes in concentrations of serum amyloid A protein, alpha 1-acid glycoprotein, haptoglobin, and C-reactive protein in feline sera due to induced inflammation and surgery. Vet Immunol Immunopathol. 1999;68(1):91-98. PMID: 10231954
- Sänger F, Unterer S, et al. C-reactive protein as a tool for monitoring response to treatment in dogs with acute hemorrhagic diarrhea syndrome. Front Vet Sci. 2022;9:1075486. PMID: 36713872
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Authored by: Migibio Clinical & Scientific Affairs, Guangzhou Magic Biotech Co., Ltd.
Reviewed by: Migibio R&D Quality Committee
Last updated: 2026-08-13
Disclosure: Migibio (Guangzhou Magic Biotech Co., Ltd.) is the manufacturer of the FIA680/FIA880 analyzers and FICT reagents referenced in this content. See our Editorial & Review Policy.