The effects of various types of anticoagulants on plasma biochemistry have been studied in humans and various animals; however, limited information exists for effects on horse plasma biochemistry. Ten clinically healthy Thoroughbred horses were blood sampled in tubes con-taining different anticoagulants as well as no anti-coagulant. The concentrations of glucose, cholesterol, triglyceride, total bilirubin, blood urea nitrogen (BUN), creatinine, total protein, albumin, calcium, inorganic phosphorus, magnesium and iron, and the activity of aspartate aminotransferase (AST), alanine aminotrans-ferase (ALT), alkaline phosphatase (ALP), creatine kinase (CK), and gamma glutamyl transferase (GGT) were mea-sured. Except for the amounts of inorganic phosphorus, magnesium, and GGT, other measured parameters were significantly lower in citrated plasma than in serum. When corrected for dilution, significant differences were seen for the amounts of glucose, cholesterol, triglyc-eride, bilirubin, calcium, iron, and the activity of ALT, ALP, and CK in citrated plasma. Most parameters did not show any difference; however, significant decreases in BUN, total bilirubin, ALT, and CK activity were seen when heparin was used as an anticoagulant. When compared with serum, using ethylenediaminetetra-acetic acid (EDTA) as an anticoagulant produced a significant difference in the amounts of measured plasmaparameters with the exception of GGT, albumin, creatinine, inor-ganic phosphorus, and triglyceride. select and use basic supplies and equipment and possess an understanding of fundamental concepts critical to any analytical procedure. 1 Anticoagulants are additives that in-hibit the clotting of blood or plasma, thereby ensuring that the concentration of the substance to be measured is changed as little as possible before the analytical process. 2 Anticoagulation is achieved either by the binding of calcium ions (ethylenediaminetetra-acetic acid [EDTA], citrate, and fluoride) or by the inhibition of thrombin (heparin). Serum from coagulated blood is the preferred specimen for clinical chemistry analysis, but plasma obtained with an appropriate anticoagulant may be an equally valid specimen and in cer-tain conditions preferable to serum. In addition, for the measurement of some trace elements, ammonia, blood pH, and blood gas analysis, whole blood sampled into an ap-propriate anticoagulant is required. 3 Heparin is the most widely used anticoagulant for clinical chemistry analysis. Conversely, EDTAis particularly useful for hematologic ex-amination and many blood samples are sent anticoagulated with EDTA to clinical laboratories. Sodium citrate solution is widely used for coagulation studies because the effect is easily reversible by the addition of Ca潧潮敫 2 . Because harvesting serum requires a 15- to 30-minute wait for completion of coagulation before centrifugation, the use of plasma expe-dites analysis in emergency situations. Furthermore, plasma yield from a given volume of whole blood is always greater than the yield of serum. 3 In addition, further biochemical

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