When measuring ammonia blood levels, which of the following might cause a false increase in this analyte?

When measuring ammonia blood levels, which of the following might cause a false increase in this analyte?

• A. The patient had two cigarettes 15 minutes prior to blood draw.
• B. The patient was fasting for hours prior to blood collection.
• C. Immediately after phlebotomy, the blood sample was maintained on ice.
• D. The patient had a steak dinner the night before the blood draw.

Answer: (D)

Ammonia in blood is highly sensitive to preanalytic factors and dietary intake. A high‑protein meal introduces more ammonia into the body as proteins are broken down, so drawing blood after a steak dinner the night before can yield a higher than true value. This dietary influence can masquerade as an elevated in vivo ammonia level, giving a false increase in the measurement. In contrast, fasting reduces dietary ammonia load, keeping the sample on ice after collection minimizes ex vivo production by cells, and smoking immediately before the draw has little reliable effect on ammonia. So the steak dinner scenario is the one that would most likely cause a false elevation.

Ammonia in blood is highly sensitive to preanalytic factors and dietary intake. A high‑protein meal introduces more ammonia into the body as proteins are broken down, so drawing blood after a steak dinner the night before can yield a higher than true value. This dietary influence can masquerade as an elevated in vivo ammonia level, giving a false increase in the measurement.

In contrast, fasting reduces dietary ammonia load, keeping the sample on ice after collection minimizes ex vivo production by cells, and smoking immediately before the draw has little reliable effect on ammonia. So the steak dinner scenario is the one that would most likely cause a false elevation.