The use of non-invasive biomarkers as predictors of disease or survival is attractive to maximize therapeutic efforts and to minimize an animal’s suffering. A 2017 Spanish study looked at the use of salivary alpha-amylase (sAA) to determine survivors versus non-survivors admitted to the Veterinary Teaching Hospital for acute abdominal disease [Contreras-Aguilar, M.D.; Martinez-Subiela, S.; Ceron, J.J., et al. Salivary alpha-amylase activity and concentration in horses with acute abdominal disease: Association with outcome. Equine Veterinary Journal 2019; DOI: 10.1111/evj.13066].

As a non-invasive biomarker for sympathetic nervous system activity from stress, sAA elevates due to tissue hypoxia, lower mean arterial pressure and pain. sAA from 33 horses admitted for acute abdomen were compared to non-painful horses admitted to the veterinary hospital for routine procedures such as castration or a health check. Of the 33 horses with abdominal pain due to gastrointestinal disease, 25 survived and eight did not.

Heart rate, respiratory rate, salivary cortisol and plasma lactate concentrations were significantly elevated in diseased horses and in non-survivors. sAA activity and concentration was significantly higher in the diseased group, and sAA concentration higher in the non-survivor diseased group. There were exceptions in this study—one horse with a strangulated inguinal hernia had high sAA activity but survived while one with low sAA activity did not. This non-survivor individual had been treated with sedatives and NSAIDs prior to hospital admittance, which might have affected sympathetic tone and sAA levels.

In general, this study demonstrates that sAA activity might serve as a useful, non-invasive biomarker of prognosis for the outcome of acute abdomen. sAA activity was elevated in horses with acute colic that did not survive compared to acute abdomen survivors.