A blood ammonia level ordered for a patient with Reye's syndrome on a clotted sample returns normal. What is the most likely explanation?

A blood ammonia level ordered for a patient with Reye's syndrome on a clotted sample returns normal. What is the most likely explanation?

• A. Inappropriate sample collection
• B. Hemolysis of the sample
• C. Delays in transport
• D. Use of an incorrect anticoagulant

Answer: (A)

Ammonia testing is highly dependent on how the sample is collected and handled. For an accurate result, ammonia must be measured in plasma from a tube containing an anticoagulant (not serum) and the specimen must be placed on ice immediately and processed quickly to prevent changes in ammonia levels. If a clotted sample (serum) is used, the clotting process and subsequent handling can alter the ammonia concentration in an unpredictable way, often masking the true elevated level you’d expect in a patient with Reye’s syndrome. In this context, a normal result most likely reflects inappropriate sample collection rather than the patient’s actual ammonia status. Other preanalytic issues, like hemolysis, transport delays, or using the wrong anticoagulant, can also affect results, but the fundamental problem here is that ammonia testing requires a plasma specimen collected with proper anticoagulation and cooling.

Ammonia testing is highly dependent on how the sample is collected and handled. For an accurate result, ammonia must be measured in plasma from a tube containing an anticoagulant (not serum) and the specimen must be placed on ice immediately and processed quickly to prevent changes in ammonia levels.

If a clotted sample (serum) is used, the clotting process and subsequent handling can alter the ammonia concentration in an unpredictable way, often masking the true elevated level you’d expect in a patient with Reye’s syndrome. In this context, a normal result most likely reflects inappropriate sample collection rather than the patient’s actual ammonia status.

Other preanalytic issues, like hemolysis, transport delays, or using the wrong anticoagulant, can also affect results, but the fundamental problem here is that ammonia testing requires a plasma specimen collected with proper anticoagulation and cooling.