In the urea method, which anticoagulant inhibits urease action?

In the urea method, which anticoagulant inhibits urease action?

• A. Sodium heparin
• B. Sodium fluoride
• C. Sodium oxalate
• D. EDTA

Answer: (B)

Urea measurement with the urease method relies on urease converting urea into ammonia, which then drives the colorimetric reaction used to quantify urea. If an anticoagulant in the sample inhibits urease, that hydrolysis step won’t occur and the assay will underestimate urea. Sodium fluoride is a known inhibitor of urease; it interferes with the nickel-containing active site of the enzyme, blocking the catalytic breakdown of urea. Therefore, a fluoride-containing anticoagulant would prevent the urease reaction from proceeding, which is why it’s the one described as inhibiting urease action. The other anticoagulants listed—heparin, oxalate, and EDTA—do not have a reliable, significant inhibitory effect on urease in this context, so they don’t produce the same interference in the urease-based urea assay.

Urea measurement with the urease method relies on urease converting urea into ammonia, which then drives the colorimetric reaction used to quantify urea. If an anticoagulant in the sample inhibits urease, that hydrolysis step won’t occur and the assay will underestimate urea.

Sodium fluoride is a known inhibitor of urease; it interferes with the nickel-containing active site of the enzyme, blocking the catalytic breakdown of urea. Therefore, a fluoride-containing anticoagulant would prevent the urease reaction from proceeding, which is why it’s the one described as inhibiting urease action.

The other anticoagulants listed—heparin, oxalate, and EDTA—do not have a reliable, significant inhibitory effect on urease in this context, so they don’t produce the same interference in the urease-based urea assay.