Ordering Recommendation

Molecular (DNA) test to confirm a diagnosis of citrullinemia type I following clinical and/or biochemical presentation. To diagnose or rule out citrullinemia type I, refer to Amino Acids Quantitative by LC-MS/MS, Plasma (2009389).

Mnemonic

ASS1 FGS

Methodology

Polymerase Chain Reaction/Sequencing

Performed

Varies

Reported

14-21 days

New York DOH Approval Status

Specimens from New York clients will be sent out to a New York DOH approved laboratory, if possible.

Specimen Required

Patient Preparation
Collect

Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).

Specimen Preparation

Transport 3 mL whole blood. (Min: 1 mL)

Storage/Transport Temperature

Refrigerated.

Unacceptable Conditions
Remarks
Stability

Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable

Reference Interval

Interpretive Data

Background Information for Citrullinemia, Type I (ASS1) Sequencing:
Characteristics:
Classic citrullinemia type I is a urea cycle disorder characterized by hyperammonemia, lethargy, vomiting, coma and neonatal death if not treated. There is also a milder, late-onset form and a form in which women have onset of severe symptoms during pregnancy or postpartum.
Incidence:
Approximately 1 in 57,000.
Inheritance:
Autosomal recessive.
Penetrance:
Variable.
Cause
: Pathogenic ASS1 gene mutations.
Clinical Sensitivity:
Approximately 96 percent.
Methodology:
Bidirectional sequencing of the entire ASS1 coding region and intron/exon boundaries.
Analytical Sensitivity and Specificity: 99 percent.
Limitations:
Diagnostic errors can occur due to rare sequence variations. Regulatory region mutations, deep intronic mutations, and large deletions/duplications will not be detected. Mutations in genes other than ASS1 are not evaluated.

This test was developed and its performance characteristics determined by ARUP Laboratories. It has not been cleared or approved by the US Food and Drug Administration. This test was performed in a CLIA certified laboratory and is intended for clinical purposes.

Counseling and informed consent are recommended for genetic testing. Consent forms are available online.

Compliance Category

Laboratory Developed Test (LDT)

Note

Hotline History

N/A

CPT Codes

81406

Components

Component Test Code* Component Chart Name LOINC
2007070 Citrullinemia, Type I (ASS1)Seq Specimen 31208-2
2007071 Citrullinemia, Type I (ASS1) Seq Interp 50398-7
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.

Aliases

  • Argininosuccinate Synthetase Deficiency (ASS1) Sequencing
  • Argininosuccinic Acid Synthetase Deficiency (ASS1) Sequencing
  • ASS Deficiency (ASS1) Sequencing
  • ASS1 Sequencing
  • CTLN1 (ASS1) Sequencing
Citrullinemia, Type I (ASS1) Sequencing (INACTIVE as of 11/15/21)