Elevated ammonia concentrations: potential for pre-analytical and analytical contributing factors.

Area of Science:

• Clinical Chemistry
• Laboratory Medicine
• Diagnostic Testing

Background:

• Hyperammonemia diagnosis is critical, but the impact of pre-analytical and analytical factors remains understudied.
• Understanding these factors is essential for accurate interpretation of ammonia test results.

Purpose of the Study:

• To investigate the distinct roles of pre-analytical and analytical variables in hyperammonemia.
• To determine the impact of sample transport and analysis delays on ammonia concentrations.

Main Methods:

• Laboratory information systems were queried for ammonia test results over a 12-month period.
• Pre-analytical (collection to receipt) and analytical (receipt to result) times were calculated.
• Data from two separate hospital laboratories were analyzed.

Main Results:

• For 3626 tests, ammonia levels were similar for results within 120 minutes of venipuncture.
• A small percentage of samples (2.7%) showed potential hyperammonemia due to transport or analysis delays.
• Findings were consistent across two different hospital laboratories.

Conclusions:

• Delays in sample transportation or analysis can lead to falsely elevated ammonia levels (pseudo-hyperammonemia).
• Unexpectedly high ammonia results necessitate a review of potential pre-analytical errors in sample handling.
• Accurate diagnosis of hyperammonemia requires attention to sample integrity and timely processing.