Carrier screening or diagnostic testing for Usher syndrome types 1F and 3 for individuals of Ashkenazi Jewish descent.
Polymerase Chain Reaction/Fluorescence Monitoring
Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).
Transport 3 mL whole blood. (Min: 1 mL)
Plasma or serum. Specimens collected in sodium heparin or lithium heparin tubes.
Ambient: 72 hours; Refrigerated: 2 weeks; Frozen: 1 month
Background Information for Usher Syndrome, Types 1F and 3 (PCDH15 and CLRN1), 2 Variants:
Characteristics: Usher syndrome type 1F is characterized by congenital, bilateral, profound sensorineural hearing loss, adolescent-onset retinitis pigmentosa and loss of vestibular function. Usher syndrome type 3 is characterized by post-lingual, progressive hearing loss, late-onset progressive vision loss due to retinitis pigmentosa and variable loss of vestibular function.
Incidence: In Ashkenazi Jewish individuals - 1 in 20,500 for Usher syndrome type 1F; 1 in 82,000 for Usher syndrome type 3.
Inheritance: Autosomal recessive.
Cause: PCDH15 and CLRN1 pathogenic variants.
Variants Tested: PCDH15 p.R245X (c.733C>T), CLRN1 p.N48K (c.144T>G).
Clinical Sensitivity: In Ashkenazi Jewish individuals - 62 percent for Usher syndrome, type 1F; 98 percent for Usher syndrome, type 3. Sensitivities unknown in other ethnicities.
Methodology: Polymerase chain reaction (PCR) and fluorescence monitoring.
Analytical Sensitivity and Specificity: Greater than 99 percent.
Limitations: Variants other than those tested will not be detected. Diagnostic errors can occur due to rare sequence variations.
Laboratory Developed Test (LDT)
|Component Test Code*||Component Chart Name||LOINC|
|2013751||Usher Syndrome Types 1F and 3, Specimen|
|2013752||Usher Syndrome Types 1F and 3, Allele 1|
|2013753||Usher Syndrome Types 1F and 3, Allele 2|
|2013754||Usher Syndrome Types 1F and 3, Interp|