LABORATORY AND CLINICAL-EVALUATION OF A CHROMOGENIC ENDOTOXIN ASSAY FOR HORSES WITH ACUTE INTESTINAL DISORDERS

In this study the laboratory and clinical performance of a chromogenic endotoxin assay for equine plasma was evaluated. The assay was sensit ive (detection limit 3 ng LPS/L plasma), reproducible (within and betw een-assay CV at 50 ng LPS/L E.coli O111:B4 LPS standard addition was 5 % and 7,5%, respectively), and not substantially affected by enhanceme nt or inhibition phenomena (recovery of an in vitro spike was 75-125% in 80% of the samples). LPS added to whole blood was rapidly inactivat ed upon incubation at 37 degrees C but not at 0 degrees C. A recently developed blood collection tube for LPS testing was found suitable, i. e. LPS-free and providing non-contaminated samples. In 48 horses suffe ring from acute abdominal diseases requiring surgical treatment, LPS l evels were significantly higher in platelet-rich plasma (PRP) than in platelet-poor plasma (PPP), and the proportional difference was relate d to the PRP platelet count(r=0.52, p<0.001, mean difference 48%, rang e 8-77%). LPS levels were also significantly higher in horses that die d or were euthanized than in surviving horses (mean 16.5 and 7.1 ng/L PRP, respectively, p<0.05). We conclude that LPS can be measured in eq uine plasma with picogram sensitivity and recommend the use of PRP ins tead of PPP for clinical LPS testing. For clinical use a decision limi t for endotoxaemia of 5 ng LPS/L PRP appeared to be inadequate. Analys is at a higher cut-off level for endotoxaemia and the evaluation of cl inical, pathological, and laboratory parameters would be more meaningf ul.