Which of the following does not need to be done when collecting, handling, and using a specimen for ammonia analysis?

• A. Avoid using a hemolyzed specimen.
• B. Collect blood in EDTA or heparin evacuated tubes.
• C. Place specimen in a 37°C water bath immediately.
• D. Advise patient not to smoke for 8 hours before blood collection.

Answer: (C)

Ammonia levels in blood are highly sensitive to pre-analytical handling because ammonia is produced and metabolized by cells after the blood is drawn. To obtain an accurate value, the specimen must be kept cold to slow in vitro production, collected in an appropriate anticoagulant to prevent clotting and allow plasma measurement, and handled in a way that minimizes cellular metabolism and contamination.

Placing the specimen in a 37°C water bath immediately would accelerate cellular activity and increase ammonia production, leading to falsely high results. That step is not needed and would bias the measurement, which is why it’s not part of proper preparation.

Avoiding a hemolyzed specimen is important because red blood cell disruption can release intracellular ammonia and falsely elevate the result. Using EDTA or heparin tubes provides a suitable anticoagulant to preserve the sample without introducing factors that would interfere with the measurement. Advising the patient not to smoke before collection helps minimize any external influences on ammonia that could skew the value.