Assessment of serum/plasma and peritoneal fluid (PF) levels of serum amyloid A (SAA), haptoglobin and fibrinogen in horses with acute abdominal disease (colic).

Methods

Blood and PF samples were collected from 75 colic horses at admission to a referral hospital and from 20 healthy control horses. SAA and haptoglobin were measured in both serum and PF. Fibrinogen was measured in plasma. Colic cases were classified according to diagnosis, treatment and outcome.  Median concentrations were compared using the Mann Whitney test.

Results

Colic horses had significantly higher median concentrations of serum SAA, PF SAA and PF haptoglobin (p<0.0001, p=0.0004 and p<0.0001, respectively) compared to controls. The correlation between serum and PF concentrations of SAA was strong (R²=0.8, p<0.0001), whereas the haptoglobin concentrations in serum and PF correlated weakly (R²=0.3, p<0.0001). Colic horses with an infectious condition such as colitis or peritonitis had significantly higher concentrations of serum SAA, PF SAA and PF haptoglobin, compared to horses with non-infectious causes of colic (p=0.0053, p=0.0167 and p=0.0278, respectively). PF haptoglobin was the only protein found to be significantly different between horses needing medical vs. surgical treatment (P=0.0146) and between survivors vs. non-survivors (P=0.0031). Serum haptoglobin and plasma fibrinogen were not statistically different in any of the groups of horses compared.

Conclusions

SAA and haptoglobin can be measured in equine peritoneal fluid similar to measurements in serum. Significant differences in the median concentrations of serum and PF SAA and PF haptoglobin were found between colic horses and healthy horses and between colic horses with and without an infectious condition. Furthermore PF haptoglobin was significantly higher in the groups of horses that needed surgical vs. medical treatment and in non-survivors vs. survivors. Assessment of SAA and haptoglobin in serum and peritoneal fluid might therefore be relevant as diagnostic and prognostic markers in colic horses.