Serum amyloid A (SAA) Is regularly used as a biomarker for detection of inflammation in horses. It would be helpful if such a biomarker could be used for survival (or not) prognostication for horses admitted to a veterinary hospital for acute colitis. A Danish study looked at SAA for its potential prognostic value in determining survival of adult horses hospitalized with acute colitis [Runge, KE.; Bak, M.; Vestergaard, A.; et al. Serum amyloid A does not predict non-survival in hospitalized adult horses with acute colitis. Vet Record Jan 2023; DOI: 10.1002/vetr.2644].
About Colitis in Horses
Typically, 90% of horses left untreated for colitis do not survive. With treatment, 80% will survive. Plasma lactate along with other cardiovascular parameters is predictive of colon viability. It could be helpful to identify individuals that have a low survival outcome prior to implementing expensive and often unsuccessful treatment that prolongs suffering. Previous studies have demonstrated that horses with medical colic tend to have higher SAA levels than those with a surgical colic condition, thus providing some information that might guide appropriate treatment and a need for surgery. In another study, horses with elevated SAA concentrations were reported to have a poorer chance of survival.
Study on SAA as Biomarker for Survivability
This retrospective study from January 2009 through December 2019 included 176 horses older than 12 months of age admitted to the veterinary teaching hospital in Copenhagen for acute colitis with diarrhea of less than 48 hours duration. Of these, 112 horses survived and were discharged (64%), while five horses died and 59 others were euthanized.
At admission, the SAA concentration for non-survivors was similar to that of survivors. The authors “expected SAA to possess prognostic value due to its excellent ability to identify inflammation, its fairly rapid concentration increase in response to inflammation, and the large dynamic concentration range reflecting the degree of underlying inflammation.” In this case, SAA was not a useful predictor for short-term survival.
Other variables—lactate, PCV, heart and respiratory rates, colic severity, mucous membrane color and WBC—showed significant differences between survivors and non-survivors. Lactate and heart rate are good indicators of cardiovascular compromise and are much more telling than the severity of inflammation as measured by SAA and the white blood cell count. In addition, age of the horse and duration of disease are other important prognostic variables.