Preferred genetic test for the detection of variants causing X-linked Alport syndrome.
- 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: Progressive renal and cochlear disease with 30-40 percent incidence of ocular involvement; 60 percent of males reach end-stage renal disease by age 30, and 85 percent have sensorineural deafness by age 40.
Incidence: Approximately 1 in 50,000 live births.
Inheritance: X-linked recessive; de novo mutations in 10-15 percent of affected males.
Penetrance: Variable, depending on mutation and sex.
Cause: Pathogenic type 4 collagen alpha chain 5 (COL4A5) mutations.
Clinical Sensitivity: Greater than 80 percent for X-linked Alport syndrome in males or females.
Methodology: Bidirectional sequencing of the entire COL4A5 coding region and intron-exon boundaries and multiplex ligation-dependent probe amplification (MLPA) to detect large COL4A5 coding region deletions and duplications.
Analytical Sensitivity & Specificity: 99 percent.
Limitations: Diagnostic errors can occur due to rare sequence variations. Regulatory region mutations and deep intronic mutations will not be detected. Breakpoints of deletions/duplications will not be determined. Mutations in genes, other than COL4A5, are not evaluated. Deletions/duplications in exons 8, 25, 40, 42, and 43 of the COL4A5 gene 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|
|2002399||ALPORT FGA Specimen||31208-2|
|2002401||Alport (COL4A5) Seq and Del/Dup Interp||53853-8|
- Alport syndrome molecular testing
- X-linked Alport syndrome molecular testing