The evidence based practice for optimal sample quality for ammonia measurement.

Area of Science:

• Clinical Chemistry
• Laboratory Medicine
• Biochemistry

Background:

• Pre-analytical variables are a primary source of variability in laboratory testing.
• Inaccurate laboratory results can lead to incorrect clinical decisions.
• Ammonia measurement is particularly susceptible to pre-analytical influences.

Purpose of the Study:

• To investigate pre-analytical factors affecting ammonia measurement.
• To quantify the impact of these factors on ammonia concentration.
• To identify key variables influencing ammonia assay accuracy.

Main Methods:

• Blood samples from 20 healthy volunteers were analyzed under various pre-analytical conditions.
• Conditions included immediate sample cooling, centrifugation temperature, measurement delay, storage temperature, and tube closure.
• Ammonia levels were measured, alongside alanine aminotransferase (ALT), gamma glutamyltransferase (GGT), and other parameters.

Main Results:

• Cooling samples immediately, centrifugation at 0°C, and storage at 4°C significantly reduced changes in ammonia concentration.
• Observed biases in ammonia levels surpassed clinical acceptance criteria.
• Multiple linear regression identified ALT, GGT, and storage temperature as significant predictors of increased ammonia.

Conclusions:

• Pre-analytical factors introduce significant errors into ammonia measurements.
• Ammonia concentration is most strongly influenced by ALT and GGT activity and storage temperature.
• Optimizing pre-analytical conditions is essential for accurate ammonia testing.