What anticoagulant is used most commonly in animal-blood collection for CBCs?

• A. Sodium heparin
• B. Potassium oxalate
• C. Potassium ethylenediamine tetraacetic acid
• D. Sodium citrate

Answer: (C)

For an accurate complete blood count, the blood must be kept from clotting while preserving the appearance and integrity of the cells. Potassium EDTA (K2EDTA) is the anticoagulant of choice because it binds calcium to stop coagulation and, importantly, preserves red blood cell shape, white blood cell details, and platelet counts over time. This makes it reliable for CBC measurements and differential counts across species, and it works well with automated counters.

Sodium heparin can be used for some chemical tests, but it can cause less stable cell morphology and may affect certain CBC parameters, so it’s not ideal for routine CBCs. Sodium citrate is great for coagulation testing (PT/aPTT) because it preserves plasma calcium for those assays, but it isn’t suitable for CBCs due to its effect on cell measurements and the need for precise plasma-to-cell ratios. Potassium oxalate is primarily used with fluoride for glucose testing and can alter cell preservation, making it unsuitable for CBCs.