Serum amyloid A and fibrinogen as markers for early detection of surgical site infection associated with internal fixation in the horse

Abstract

The objective of this study was to determine the diagnostic ability of serum amyloid A (SAA) and fibrinogen for early detection of surgical site infection (SSI) after equine internal fixation. Horses undergoing internal fixation for fracture, arthrodesis, or osteotomy with internal fixation for limb deformity were included in the study. SAA and fibrinogen were measured on blood samples preoperatively and on days 1, 3, 5, 7, 10, and 14 postoperatively. Statistical analysis included use of Spearman's rank correlation, logistic regression, and calculating the area under the receiver operating characteristic (ROC) curve. SAA and fibrinogen measurements were both associated with SSI, with SAA being considered an excellent marker (area under the ROC curve 0.8) and fibrinogen being considered acceptable (<0.8). As the amount of time postoperatively increased, SAA elevations indicated a higher likelihood of SSI (area under the ROC curve 0.8 compared with fibrinogen 0.7). SAA and fibrinogen were predictive markers of SSI and SAA is of greater diagnostic utility when compared with fibrinogen. Persistent elevations of SAA postoperatively are associated with the development of SSI. Serial monitoring of SAA can be used to help predict the development of SSI in horses undergoing internal fixation. This may lead to earlier suspicion, and therefore recognition and treatment of SSI.

Current treatment and prevention of orthopaedic infections in the horse

“…Serial monitoring of blood SAA can be used to effectively monitor response to treatment (Haltmayer et al, 2017). Thurston et al (2022) also found that serial monitoring of fibrinogen and SAA can be successfully used to monitor horses for development of infection following internal fixation of long bones.…”

“…Minocycline should be considered for treatment of synovial infections due to accumulation of the drug in synovial fluid (Schnabel et al, 2012). Recent investigations indicate the reliability of serial serum amyloid A (SAA) monitoring as a predictor for surgical site infection in cases of fracture, arthrodesis or osteotomy (Thurston et al, 2022). Observance of a decreasing SAA by 1 week post operatively has been correlated with a lower likelihood for developing a surgical site infection and an indication to cease systemic antimicrobial therapy (Thurston et al, 2022).…”

“…These administration routes decrease the required dose and directly target infected tissue. Systemic monitoring, including quantification of fibrinogen and serum amyloid A, can help provide objective data about the clinical progression of orthopaedic infections, offering assistance in the decision to continue or cease antimicrobial therapy (Thurston et al, 2022). Moving forward, more research is needed to determine whether shorter durations of antimicrobial therapy are effective as this will help avoid extended use of drugs beyond resolution of infection.…”