Appropriate test when clinical/family history is classic for HHT.
- Patient Preparation
- Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).
- Specimen Preparation
- Transport 3 mL whole blood. (Min: 2 mL)
- Storage/Transport Temperature
- Unacceptable Conditions
- Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable
Characteristics: Recurrent nosebleeds, telangiectases (mouth, face, hands, GI tract), and arteriovenous malformations (lung, brain, liver, spine).
Inheritance: Autosomal dominant.
Penetrance: Approaches 100 percent by age 40.
Cause: Mutations in endoglin (ENG), activin A receptor type II-like 1 (ACVRL1 or ALK1), SMAD4 or other unidentified gene(s).
Clinical Sensitivity: Approximately 85 percent
Methodology: Bidirectional sequencing of ENG and ACVRL1 - all exons and exon/intron boundaries, including the 5' untranslated region of ENG; Multiplex Ligation-dependent Probe Analysis (MLPA) to detect large ENG and ACVRL1 gene deletion/duplication; oligonucleotide probes cover all ENG and ACVRL1 coding exons.
Analytic Sensitivity: 99 percent for sequencing and 90 percent for MLPA.
Analytic Specificity: 99 percent for sequencing and 98 percent for MLPA.
Limitations: Diagnostic errors can occur due to rare sequence variations. The breakpoints of large deletions/duplication cannot be determined. Regulatory region, intronic mutations, and mutations in genes other than ENG and ACVRL1 will not be detected.
Counseling and informed consent are recommended for genetic testing. Consent forms are available online.
|Component Test Code*||Component Chart Name||LOINC|
|2009010||HHT Seq/DelDup Interpretation|
|2009011||HHT Seq/DelDup Specimen|