Can blood serum amyloid A concentrations in horses differentiate synovial sepsis from extrasynovial inflammation and determine response to treatment?

BACKGROUND: Serum amyloid A (SAA) concentrations in blood and synovial fluid of horses with synovial sepsis have diagnostic value. Studies suggest serial blood SAA measurements could act as a prognostic indicator. This study evaluated the use of serial blood SAA concentrations for monitoring of horses with synovial sepsis. METHODS: A prospective clinical trial was performed of horses referred to a single hospital with synovial sepsis that survived (n=17), synovial sepsis that were euthanised (n=5), non-septic intrasynovial pathologies (n=14) or extensive extrasynovial lacerations (n=5). SAA concentrations were determined on admission and every 24 hours thereafter. The area under the concentration–time curve from 0 to 144 hours of each group was compared by Kruskal-Wallis and post hoc Dunn’s tests (P<0.05). RESULTS: Significant difference in mean blood concentration of SAA was found between synovial sepsis that survived and non-septic pathologies in the first 48 hours, as well as between non-septic intrasynovial pathologies and non-responsive sepsis requiring euthanasia. No difference was found between extensive extrasynovial lacerations and any septic group. CONCLUSIONS: While serial blood SAA is useful for monitoring clinical response of intrasynovial septic pathologies, interpretation should consider other clinical findings since blood SAA is not a specific marker for synovial sepsis.