When and how should we measure plasma ammonia?

Area of Science:

• Clinical Chemistry
• Paediatric Medicine
• Metabolic Disorders

Background:

• Hyperammonaemia presents significant morbidity and mortality risks.
• Early diagnosis is critical as it is often treatable and can be genetically determined.
• Plasma ammonia measurement is essential in paediatric, especially neonatal, settings for diagnosing inherited metabolic disorders.

Purpose of the Study:

• To highlight the importance of urgent plasma ammonia measurement in neonates.
• To emphasize the need for readily available and timely laboratory investigations for suspected metabolic disorders in infants.
• To guide the interpretation and monitoring of plasma ammonia levels in paediatric patients.

Main Methods:

• Utilizing specific ion-selective electrode systems or automated enzyme methods for reliable plasma ammonia measurement.
• Advocating for quantitative assays over screening methods like microdiffusion.
• Integrating urgent plasma ammonia testing into routine laboratory services for neonatal and paediatric units.

Main Results:

• Plasma ammonia levels require careful interpretation considering patient age, maturity, clinical status, and other investigations.
• Frequent monitoring of plasma ammonia is often necessary during treatment.
• Current diagnostic thresholds may need adjustment to prevent misdiagnoses.

Conclusions:

• Plasma ammonia measurement is a critical diagnostic tool in paediatric medicine, particularly for neonates with suspected inherited metabolic disorders.
• Laboratories supporting neonatal and paediatric units must offer urgent, reliable plasma ammonia testing.
• Lowering the threshold for accepting requests is essential to improve diagnostic accuracy and patient outcomes.