Measurement of serum amyloid A in the neonatal foal using a latex agglutination immunoturbidimetric assay: determination of the normal range, variation with age and response to disease.
Authors: Stoneham S J, Palmer L, Cash R, Rossdale P D
Journal: Equine veterinary journal
Summary
# Editorial Summary Serum amyloid A (SAA) is an acute-phase protein that rises rapidly in response to infection and inflammation, making it a potentially valuable diagnostic marker in neonatal foals where early identification of septicaemia or focal infection is critical for survival. Stoneham and colleagues used latex agglutination immunoturbidimetry to establish baseline SAA concentrations in 226 clinically healthy Thoroughbred foals over the first three days of life, finding that levels peak on day 2 (significantly higher than day 1; P<0.0001) with a 95th percentile threshold of 27.1 mg/l. When compared against control foals, those with confirmed septicaemia or focal infection showed markedly elevated SAA concentrations (P<0.0001), whilst foals with failure of passive transfer or non-infectious disease did not differ significantly from healthy controls—a distinction that positions SAA as a reasonably specific marker for bacterial infection rather than a general indicator of neonatal compromise. Notably, SAA concentrations exceeding 100 mg/l were highly suggestive of active infection in young foals, offering veterinarians an objective laboratory aid to support clinical decision-making about antimicrobial therapy in the critical early hours when sepsis carries the highest mortality risk. This assay therefore warrants consideration as part of the diagnostic workup for sick neonates, particularly where clinical signs are ambiguous or where rapid confirmation of infection status would influence treatment intensity.
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Practical Takeaways
- •SAA >100 mg/l in neonatal foals should raise strong suspicion of septicaemia or focal infection and warrant immediate further investigation and treatment
- •Establishing baseline SAA concentrations by age (Days 1-3) helps clinicians interpret results correctly, as normal levels are significantly elevated on Day 2 postpartum
- •SAA measurement via latex agglutination assay provides a rapid, accessible diagnostic aid to differentiate infectious from noninfectious neonatal conditions, supporting early intervention decisions
Key Findings
- •Serum amyloid A (SAA) levels are significantly highest on Day 2 postpartum in healthy neonatal foals (P<0.0001), with 95th percentile of 27.1 mg/l across Days 1-3
- •SAA concentrations >100 mg/l are highly suggestive of infection (septicaemia or focal infection) in neonatal foals, with statistically significant difference from controls (P<0.0001)
- •Latex agglutination immunoturbidimetric assay can differentiate infectious disease from failure of passive transfer and noninfectious disease in foals
- •No statistically significant difference in SAA levels between controls and foals with failure of passive transfer or noninfectious disease