C9orf72 Expansion Assay
Test Mnemonic
C9ORF
CPT Codes
- 81479 - QTY (1)
Performing Laboratory
Prevention Genetics
FDA Category
Laboratory Developed Test
Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 5 mL | Whole blood | EDTA (Lavender) | Ambient |
Alternate Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 5 mL | Whole blood | ACD A or B (Yellow) | Ambient | ||
| Other | Extracted DNA | EDTA (Lavender) | Ambient | 15 ug extracted DNA at a concentration of 20 ug/mL is required |
Minimum Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 2 mL |
Stability
| Environmental Condition | Description |
|---|---|
| Ambient | 48 hours |
| Refrigerated | 1 week |
| Frozen | Unacceptable |
Days Performed
Upon receipt
Turnaround Time
15 days
Methodology
| Name | Description |
|---|---|
| Repeat-primed PCR and Fluorescent Fragment-Length Assay |
Reference Range
Clinical Info
The function of C9orf72 is unknown at this time. Nonetheless, nuclear RNA foci were detected in affected tissues of patients with expanded GGGGCC repeats, suggesting defective RNA processing (Rademakers et al. Nat Rev Neurol 8(8):423-434, 2012). The repeat-primed PCR test is used as a screening method for the presence or absence of a pathogenic GGGGCC hexanucleotide repeat expansion located in the first intron of C9orf72. Of note, this test is not designed to determine the number of GGGGCC repeats in alleles carrying the pathogenic expansion (Warner et al., 1996; Renton, 2011).