Consider ordering if no variants are detected with OTC gene sequencing and suspicion for OTC deficiency remains. Determine carrier testing for individuals who have a family history of a deletion or duplication in the OTC gene.
- Patient Preparation
- Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).
- Specimen Preparation
- Transport 3 mL whole blood. (Min: 1 mL)
- Storage/Transport Temperature
- Unacceptable Conditions
- Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable
Characteristics: Classic OTC deficiency is a urea cycle disorder characterized by hyperammonemia, cyclical vomiting, seizures, lethargy, coma and neonatal death if not treated. Clinical presentation varies widely in females, and some males can have non-classical forms.
Incidence: Approximately 1 in 20,000.
Penetrance: Variable depending on sex and mutation.
Cause: Pathogenic OTC gene mutations.
Clinical Sensitivity: Approximately 10 percent.
Methodology: Multiplex ligation-dependent probe amplification (MLPA) to detect large OTC coding region deletions/duplications.
Analytical Sensitivity and Specificity: 99 percent.
Limitations: Diagnostic errors can occur due to rare sequence variations. Single base pair substitutions, small deletions/duplications, regulatory region mutations, and deep intronic mutations will not be detected. The breakpoints of large deletions/duplications will not be determined.
|Component Test Code*||Component Chart Name||LOINC|
|2004893||OTC Deficiency (OTC) Del/Dup Specimen|
|2004894||OTC Deficiency (OTC) Del/Dup Interp|
- OTC deletion/duplication assay
- Urea Cycle Defect