Clinical Lab Handbook

Container/Tube: Light green-top (lithium heparin) gel tube-or dark green (lithium heparin) non-gel

Transport Temperature: On Ice

Collection Instructions: Needs to be put on ice and spun down within 15 minutes of collection. If the non-gel tube is used, plasma must be transferred to pour off tube immediately following centrifugation. Forward promptly. If there is a delay in transport of ≥3 hours, send specimen frozen in plastic vial. Hemolyzed specimen is not acceptable.

The VITROS AMON Slide is a multilayered, analytical element coated on a polyester support. A drop of patient sample is deposited on the slide and is evenly distributed by the spreading layer to the underlying layers. Water and nonproteinaceous components travel to the underlying buffered reagent layer, and the ammonium ions are converted to gaseous ammonia. The semipermeable membrane allows only ammonia to pass through and prevents buffer or hydroxyl ions from reaching the indicator layer. After a fixed incubation period, the reflection density of the dye is measured using the white background of the spreading layer as a diffuse reflector.

Ammonia is a waste product of protein catabolism; it is potentially toxic to the central nervous system. Increased plasma ammonia may be indicative of hepatic encephalopathy, hepatic coma in terminal stages of liver cirrhosis, hepatic failure, acute and subacute liver necrosis, and Reye’s syndrome. Hyperammonemia may also be found with increasing dietary protein intake.

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