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C3 Glomerulopathy (C3G) Genetic Panel

Justification

Genetics can help confirm a C3G diagnosis which can be challenging due to technical issues with immunofluorescence. Furthermore, since there is no disease-specific treatment for C3G, genetics may help treatment decisions; for example, patients with mutations may respond more poorly to mycophenolate mofetil than those with nephritic factors.

STAT: < 48 hours (M-F)

NGS, RT-PCR

Draw Tube: Purple Top

Sample Type: EDTA Whole Blood

DRAW KITS AVAILABLE

Specimen Requirements

Sample Type Volume Required Minimum Volume Stability
PREFERRED EDTA Whole Blood 3mL 1mL Room Temp.: 1 month
Refrigerated: 1 month
ALTERNATIVE Cheek swab 2 swab - Room Temp.: 1 month
Refrigerated: 1 month
REJECTION CRITERIA Sample contamination; sample compromised
SPECIAL INSTRUCTIONS Post bone marrow transplant (post-BMT) patients require a cheek swab sample to test the transplant recipient; post-BMT patients require a venous blood sample to test the bone marrow donor.

General Information

METHODOLOGY NGS, RT-PCR
STAT TAT < 48 hours (M-F)
STAT TAT Performance > 90% of results released in 48 hours
ROUTINE TAT < 5 days (M-F)
ALTERNATIVE NAMES dense deposit disease (DDD), C3 glomerulonephritis (C3GN), CFHR5 nephropathy, membranoproliferative glomerulonephritis (MPGN), complement-mediated HUS, cm-HUS
DESCRIPTION C3G comprises a group of rare kidney diseases caused by complement dysregulation. Genes sequenced: CFB, CFH, CFI, MCP, C3, CFHR5. CFHR5 is checked for the Cypriot duplication by RTPCR. Sanger sequencing may be used to confirm variants as needed.
LIMITATIONS This test will not detect variants located outside of the targeted DNA regions. This test is not optimized to detect chimerism or somatic mosaicism. This test will detect small indels but may miss larger deletions or duplications. Balanced structural variants will not be detected unless specifically targeted by a custom PCR assay.
NORMAL RANGE Interpretation: Negative
ASSOCIATED TESTING -
REFERENCES

1. Smith RJH et al. C3 glomerulopathy – understanding a rare complement-driven renal disease. Nat Rev Nephrol. 2019 Mar;15(3):129-143.

2. Pickering MC et al. C3 glomerulopathy: consensus report. Kidney Int. 2013;84, 1079–1089.
SAMPLE REPORT Upon request
NEW YORK STATE APPROVED No

Test Codes

ORDER CODE P1214
CPT CODE 81479x6
LOINC CODE 51779-7