Ammonia
(NH3, NH4)

Sample type:

Plasma EDTA (EDTA is the only acceptable anticoagulant)

Uses:

• To detect elevated concentrations of ammonia in the blood

• to help diagnose severe liver disease and certain genetic urea cycle disorders

• to investigate changes in consciousness

• to help diagnose hepatic encephalopathy and Reye’s syndrome

Precautions:

• Tourniquet (Do not use tourniquet).

• Undefiled tubes (Tubes should be full).

• Avoid prolonged exposure to air.

• Smoking should be avoided prior to sampling.

• After collection, gently invert tube 8-10 times.

• Specimens should be put on ice immediately after collection.

• Centrifuge at refrigerated temperature (4 degrees C).

• Aliquot plasma into plastic screw-top tube. Keep on ice.

• Freeze plasma within 2 hours of collection.

• Specimen type plasma EDTA Frozen (preferred) 7 days Refrigerated 2 hours.

Interference factor:

• Hemolysis increases ammonia levels because the red blood cells have about three times the ammonia level content of plasma.

• Muscular exertion can increase levels.

• Cigarette smoking can product significant increases in levels within 1 hour of inhalation.

• Ammonia levels may be factitiously increased if the tourniquet is too tight for a long period.

• Drugs that may cause increased ammonia levels include: acetazolamide, alcohol, ammonium chloride, barbiturates, diuretics (loop, thiazide), narcotics, parenteral nutrition, and valproic acid.

• Drugs that may cause decreased levels include: broad-spectrum antibiotics (e.g., neomycin), lactobacillus, lactulose levodopa, and potassium salts.

• Anticoagulants such as citrate, oxalate, ammonium heparin, or sodium fluoride (may cause spuriously high results).

• lithium heparin may cause spuriously low results.

• Ammonia may be generated during clotting.

• Hemolysis which increases plasma ammonia.

Pre-analytical errors:

Uses anticoagulants such as (citrate, oxalate, ammonium heparin, or sodium fluoride lithium heparin), Clotted specimen; gross hemolysis

Corrective of action:

The sample must be rejected and anther sample be obtained.

Post analytical errors:

Write the wrong name in the report or the wrong results.

The corrective action:

If the report is not delivered to the patient and this error is discovered, the correct result or the correct name must be written, but if the report is delivered to the patient, you must communicate with him, apologies to him, and tell him that an error has occurred and replace it with the correct report.

Reference Range:

Adults: 10-80 mcg/dL (6-47 µmol/L)

Neonates, 0 to 10 days (enzymatic): 170-341 mcg/dL (100-200 µmol/L)

Infants and toddlers, 10 days to 2 year (enzymatic): 68-136 mcg/dL (40-8- micromole/L)

Children, older than 2 years (enzymatic): 19-60 mcg/dL(11-35 µmol/L)