Comparison of lipopolysaccharides and soluble CD14 measurement between clinically endotoxaemic and nonendotoxaemic horses

Summary Reasons for performing study Clinically useful biomarkers are needed for early identification of endotoxaemic horses. Soluble CD14 (sCD14) is amplified early in response to inflammatory signals, including bacterial lipopolysaccharide (LPS), and may prove a useful biomarker for clinical endotoxaemia. Objectives The aim of this study was to determine if sCD14 could serve as a more reliable biomarker of the clinical signs of endotoxaemia, compared to measuring LPS alone. Study design Prospective observational study in horses at a veterinary teaching hospital. Methods Plasma samples were collected from 20 healthy horses and 35 horses presenting for emergency evaluation. Horses were classified as clinically endotoxaemic, using previously established criteria, if they had a heart rate >70 beats/min, packed cell volume >45% and/or a lesion likely to result in endotoxaemia. Soluble CD14 was measured using a cytometric bead‐based assay and LPS was measured using a Limulus amoebocyte lysate (LAL) assay. Results Soluble CD14 was higher in horses classified as clinically endotoxaemic (median 1102 ng/ml, interquartile range 439 ng/ml), compared to clinically nonendotoxaemic (median 692 ng/ml, interquartile range 455 ng/ml, P = 0.03. There was no difference in LPS concentrations between clinically nonendotoxaemic (median 5.4 endotoxin units [EU]/ml, interquartile range 5 EU/ml) and endotoxaemic horses (median 7.2 EU/ml, interquartile range 17 EU/ml, P = 0.2). There was no correlation between sCD14 and LPS values in paired serum samples. LPS and sCD14 values were used to generate a receiver operating characteristic curve. The area under the curve for LPS and sCD14 was <0.7, suggesting that sCD14 and LPS were poor predictors of clinical endotoxaemia for the horses in this study. Conclusions Further investigation is warranted to assess the utility of sCD14 measurement as a clinically useful biomarker to identify endotoxaemia in horses.