In routine practice, when PON‐1 activity upon admission is lower than the RI, according to our data, SIRS is always present, as demonstrated also by the Fisher test, and the likelihood for the horse to not survive is 2.40 to 3.89 times higher than the likelihood to respond to treatment, supporting the hypothesis that PON‐1 activity may provide useful information in clinical practice. The gene discussed is PON1; the disease is systemic inflammatory response syndrome.