Serum amyloid A and haptoglobin concentrations in serum and peritoneal fluid of healthy horses and horses with acute abdominal pain.

BACKGROUND: Peritoneal fluid (PF) analysis is a valuable diagnostic tool in equine medicine. Markers such as serum amyloid A (SAA) and haptoglobin (Hp) could facilitate the diagnosis of inflammatory abdominal conditions.
OBJECTIVES: The objectives were to (1) establish reference intervals (RI) for SAA and Hp in serum and PF in healthy horses, (2) compare SAA and Hp concentrations between healthy horses and horses with colic, and (3) to assess the correlation between serum and PF concentrations.
METHODS: Serum amyloid A and Hp concentrations were determined by automated assays in prospectively enrolled healthy reference horses and horses with colic. RIs were calculated, group concentrations were compared by Student's t-test, and Pearson's correlation for serum and PF concentrations were determined.
RESULTS: In healthy horses (n = 62) the measurements for SAA were below the detection limit (0.5 mg/L) in 94% of serum samples and 98% of PF samples. Horses with colic (n = 61) had statistically significantly increased SAA concentrations in serum (P < .0001) and PF (P = .0013). While PF Hp concentrations were increased in horses with colic the serum concentrations of Hp were decreased (P < .0001). There was a strong correlation between paired serum and PF SAA concentrations (n = 94, R = .72, P < .0001), whereas the correlation between paired serum and PF Hp was weak (n = 94, R = .22, P = .0382). Finally, horses with colic tended to have serum SAA and PF Hp concentrations above the RIs.
CONCLUSIONS: With the apparent difference between healthy horses and horses with colic and the presently established RIs, serum SAA and PF Hp concentrations represent potential valuable diagnostic markers for inflammatory abdominal conditions in that species.