What is the alternative for BUN enzymatic tests as sodium fluoride inhibits urease?

• A. Sodium fluoride
• B. Iodoacetate
• C. Ethanol
• D. Glucose

Answer: (B)

The main idea is to prevent microbial activity that could alter urea levels after blood collection without blocking the urease activity used in the assay. In the enzymatic BUN method, urease hydrolyzes urea to ammonia, which is then measured. Sodium fluoride inhibits urease, so it cannot be used as a preservative in samples intended for this method. To protect the sample from bacterial urease without inhibiting the urease added in the assay, an alternative preservative such as iodoacetate is used. Iodoacetate inhibits bacterial enzymes by reacting with thiol groups, limiting post-collection ammonia production, while leaving the assay’s urease functional. The other options either would still interfere with the enzymatic reaction or are not effective preservative strategies for this purpose.