Stabilizing specimens for routine ammonia testing in the clinical laboratory.

Area of Science:

• Clinical Chemistry
• Biochemistry
• Laboratory Medicine

Background:

• In vitro deamination of blood generates ammonia, necessitating rapid sample processing.
• Current ammonia testing requires samples to be kept on ice and analyzed within one hour.
• A novel method was developed to stabilize blood specimens for ammonia analysis, improving sample integrity.

Purpose of the Study:

• To develop and evaluate a method for stabilizing plasma ammonia specimens.
• To inhibit in vitro ammonia generation in blood samples.
• To extend the time frame for reliable ammonia testing.

Main Methods:

• Plasma separation followed by addition of cycloserine or sodium borate/l-serine.
• Inhibition of deamination and removal of residual platelets.
• Incubation of samples at room temperature, 4°C, or -80°C, with ammonia measurement at various time points.

Main Results:

• Untreated samples at 4°C showed rapid ammonia increase, especially with high enzyme activity (ALT/GGT).
• Sodium borate/l-serine significantly reduced ammonia increase at 4°C in both normal and high enzyme activity samples.
• -80°C storage also effectively preserved specimens, showing minimal ammonia increase.

Conclusions:

• Combining sodium borate/l-serine with refrigeration stabilizes plasma ammonia specimens for over 12 hours.
• This method offers a reliable approach to prevent ammonia degradation in collected blood samples.
• The findings support extended stability for ammonia testing, reducing the need for immediate analysis.