Use of serum amyloid A and other acute phase reactants to monitor the inflammatory response after castration in horses: a field study

Reasons for performing the study: Early recognition of excessive inflammation and infectious complications after surgery, leading to early institution of therapy, reduces post operative discomfort and facilitates recovery. Because serum amyloid A (SAA) is a highly sensitive marker of inflammation, measurements of SAA and other acute phase reactants in the equine surgical patient may be valuable in assisting clinical assessment of post operative inflammation. Objectives: To investigate changes in inflammatory markers after castration and to correlate levels of acute phase reactants with clinical severity of inflammation after castration. Methods: Leucocyte numbers and blood levels of iron, SAA and fibrinogen were determined before castration and on Days 3 and 8 post operatively in 2 groups of horses; Group I (n = 11) had mild post operative inflammation and an uncomplicated recovery and Group 2 (n = 7) had local clinical signs of moderate to severe inflammation. Results: Both groups had elevated serum SAA levels at Day 3 post operatively. In Group I concentrations had returned to preoperative levels by Day 8, whereas in Group 2 concentrations remained elevated. Plasma fibrinogen concentrations in serum increased to equal levels in both groups and stayed elevated throughout the study period. Serum iron concentrations of Group I did not change in response to castration, whereas concentrations in Group 2 decreased below preoperative levels on Day 8. Leucocyte numbers remained unchanged during the post operative period in both groups. Conclusions: Serum SAA and iron profiles reflected the course of inflammation and their levels correlated with the clinical severity of inflammation. In contrast, fever and changes in leucocyte numbers, which are usually considered to be hallmarks of inflammation and infection, were not useful for monitoring post operative recovery. Potential relevance: Measurements of SAA and iron may improve post operative monitoring. As sustained inflammation may indicate that the surgical wound has become infected, SAA and iron measurements may facilitate early recognition and hence early treatment of infection.