Effects of Blood Contamination on Peritoneal D‐Dimer Concentration in Horses with Colic

Background: Peritoneal D‐Dimer concentration can be determined to assess peritoneal fibrinolysis activity in horses with gastrointestinal disorders. However, blood contamination of peritoneal fluid may occur during collection and could alter peritoneal D‐Dimer concentration. Hypothesis/Objectives: Blood contamination in peritoneal fluid does not affect interpretation of peritoneal D‐Dimer concentration in horses with colic. Animals: Thirty‐four horses with colic and 4 healthy horses. Methods: Peritoneal fluid and blood samples were simultaneously collected upon admission. Then, peritoneal fluid was serially contaminated with the horse's own blood; final contaminations corresponded to 1, 5, 10, and 20% of blood in peritoneal fluid. D‐Dimer concentration was determined in blood, peritoneal fluid, and contaminated peritoneal fluid samples. Data were analyzed using a longitudinal linear model and a generalized estimating equations analysis to assess the quantitative and qualitative variations of the effect of blood contamination on peritoneal D‐Dimer concentration. Results: Peritoneal D‐Dimer concentration was only quantitatively affected when peritoneal fluid was contaminated at 20% of blood. However, when using increasing cut‐off values of peritoneal D‐Dimer concentration (100, 2,000, 8,000, and 16,000 ng/mL), this effect disappeared at the highest cut‐off values (8,000 and 16,000 ng/mL). When peritoneal fluid contamination was grouped as “minimally contaminated” (≤1% of blood) and “highly contaminated” (≥5% of blood), no significant differences on D‐Dimer concentration between both groups at each cut‐off value were observed. Conclusions and Clinical Importance: Although quantitative results of peritoneal D‐Dimer concentration could be affected by high levels of blood contamination (≥20%), interpretation of increased peritoneal fibrinolytic activity was not significantly affected.