The diagnosis of a urea cycle disorder is based on the evaluation of clinical, biochemical, and molecular data, including:
- Plasma ammonia level: The sample must be placed immediately on ice and run STAT, or false elevations can occur. Obtaining Accurate Ammonia Levels
- Plasma quantitative amino acid analysis can be used to help diagnose a specific urea cycle disorder.
- Urinary orotic acid is measured to distinguish CPSI deficiency and NAGS deficiency from OTC deficiency.
- Molecular genetic testing.
- Plasma ammonia measurement is a simple yet important screening in the ED for patients with unexplained stupor or delirium. Recognizing the symptoms of the disease is often delayed and/or mistaken. Obtaining Accurate Ammonia Levels
- Although UCD is usually identified in early childhood, partial or mild forms may not be recognized until unmasked by an environmental trigger that can lead to catastrophic hyperammonemic crisis.
- Altered consciousness should always lead to blood ammonia measurement.
- Ornithine transcarbamylase deficiency should be suspected in adult patients who develop recurrent hyperammonemia and encephalopathy following bariatric surgery.
- The diagnosis of NAGS or OTC deficiency should be considered in nonhepatic adult patients with hyperammonemic coma, particularly if they have a history of protein avoidance and neurological symptoms.
Treatment options for Urea Cycle Disorders
New England Consortium of Metabolic Programs Treatment Guidelines
Rare Diseases Clinical Research Network Urea Cycle Disorders Consortium
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