Please ensure JavaScript is enabled for purposes of website accessibility Laboratory Testing for Urea Cycle Disorders | For HCPs

Laboratory Testing Laboratory Testing for Urea Cycle Disorders

Patients with a urea cycle disorder (UCD) require regular monitoring of their labs because their ammonia levels may become dangerously high.1,2 Measuring ammonia, however, can be challenging and may result in falsely elevated ammonia if blood is not drawn correctly.2,3

Careful collection and processing can help ensure reliability of results.3

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Careful collection and processing can help ensure reliability of results.3

Consider the following guidance for accurate ammonia testing3,4

  • Collect free-flowing venous or arterial blood
  • Ensure the patient is relaxed as stress can cause spurious increases in ammonia levels
  • Draw blood into a prechilled vacuum tube and place it on ice for transport
  • At the laboratory, blood should be separated within 15 minutes and analyzed immediately

Ammonia testing is routinely available at most hospitals. Learn more about the correct procedures for accurate ammonia testing.

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Phenylbutyrate Metabolite Testing for Therapeutic Monitoring

  • In addition to ammonia, glutamine can be used as an indicator of metabolic control in patients with a UCD5,6
  • Phenylbutyrate metabolite testing measures the drug’s level to ensure it is at an ideal therapeutic dosage. It can be used in conjunction with ammonia and glutamine levels to help guide management decisions and optimal treatment7-9 
  • Additional labs may be appropriate for each unique patient and UCD subtype
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Order a No-Cost Metabolite Test

This test is vital for patients with a UCD

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Access Resources for You and Your Patients

Review important information you can share with your patients and practice

  • References

    1. Pei KJ, Pei KJ, Rajikan RB, et al. Growth and nutritional status of children with urea cycle defects (UCD): a 6-months follow up study in Institute of Pediatric, Hospital Kuala Lumpur. Int J Clin Nutr. 2014; 2(3):41-52. 2. Häberle J, Boddaert N, Burlina A, et al. Suggested guidelines for the diagnosis and management of urea cycle disorders. Orphanet J Rare Dis. 2012;7:32. 3. Barsotti RJ. Measurement of ammonia in blood. J Pediatr. 2001;138 (suppl 1):S11-S20. 4. Hawke L. Ammonia (Plasma, Blood). Association of Clinical Biochemistry; 2012. 5. Ah Mew N, Simpson KL, Gropman AL, Lanpher BC, Chapman KA, Summar ML. Urea Cycle Disorders Overview. In: Adam MP, Mirzaa GM, Pagon RA, et al., eds. GeneReviews®. Seattle (WA): University of Washington, Seattle; April 29, 2003. 6. Lee B, Diaz GA, Rhead W, et al. Glutamine and hyperammonemic crises in patients with urea cycle disorders. Mol Genet Metab. 2016;117(1):27-32. 7. Mokhtarani M, Diaz GA, Rhead W, et al. Elevated phenylacetic acid levels do not correlate with adverse events in patients with urea cycle disorders or hepatic encephalopathy and can be predicted based on the plasma PAA to PAGN ratio. Mol Genet Metab. 2013;110(4):446-453. 8. Mokhtarani M, Diaz GA, Rhead W, et al. Urinary phenylacetylglutamine as dosing biomarker for patients with urea cycle disorders. Mol Genet Metab. 2012;107(3):308-314.12. 9. Häberle J, Burlina A, Chakrapani A, et al. Suggested guidelines for the diagnosis and management of urea cycle disorders: first revision. J Inherit Metab Dis. 2019;42(6):1192-1230.