Which anticoagulant is used for enzyme testing?

• A. Heparin
• B. EDTA
• C. Citrate
• D. Oxalate

Answer: (A)

Enzyme testing depends on the enzyme’s ability to function with its required ions and cofactors. Chelating anticoagulants remove these essential ions from the sample. EDTA, citrate, and oxalate bind calcium (and often other divalent cations), which many enzymes need to act properly, so they can alter or inhibit enzyme activity and distort results. Heparin prevents clotting without stripping away these ions, so the enzyme activities in the sample stay closer to their true levels. That compatibility with preserving enzymatic activity is why heparinized plasma is preferred for enzyme testing.