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Test Code RB1 Eval RB1 Gene Evaluation

Important Note

This test includes retinoblastoma RB1 gene sequence analysis with reflex to deletion/duplication on blood only.  For RB1 testing on tumor tissue, please contact Laboratory Genetic Counselors at 206-987-5400 for further guidance.

Clinical System Name

RB1 Gene Evaluation

Synonyms

Retinoblastoma

Description

Retinoblastoma (Rb) is a malignant tumor of the developing retina that occurs in children, usually before age five years. Rb occurs in cells that have cancer-predisposing mutations in both copies of the gene RB1. Rb may be unifocal or multifocal. About 60% of affected individuals have unilateral Rb with a mean age of diagnosis of 24 months; about 40% have bilateral Rb with a mean age of diagnosis of 15 months. Individuals heterozygous for a cancer-predisposing mutation in one RB1 allele are said to have a germline mutation and thus have a heritable predisposition to Rb. They also have an increased risk of developing non-ocular tumors. RB1 is the only gene in which mutations are known to cause heritable predisposition to retinoblastoma.

Sample Requirements

Specimen: Whole Blood

Container(s): Lavender Top/EDTA

Preferred Vol: 10 mL

Minimum Vol: 4 mL

 

Specimen: DNA

Container(s): Sterile plastic tube

Preferred Vol:

Minimum Vol:

Notes: Please include the concentration.

 

Notes: Signed informed consent is required. 

 

Processing Instructions

Reject due to:

Spin: N

Aliquot: N

Temp: 2-8 C

Storage location: Affix large Cerner labels to tubes and place in refrigerator send-outs rack.

 

Off-site collection: Send whole blood refrigerated.

Stability

Specimen Type Temperature Time
Whole blood Room temp 3 d
Whole blood Refrigerated 7 d
Whole blood Frozen N
Extracted DNA Room temp 3-4 d
Extracted DNA Refrigerated 1 y
Extracted DNA Frozen Indefinitely

 

Availability

STAT TAT
N 8-12 w

 

Performing Laboratory

Genetic Diagnostic Laboratory, University of Pennsylvania School of Medicine

 

Department:  Genetic Diagnostic Laboratory, University of Pennsylvania School of Medicine, 415 Anatomy-Chemistry Building, 3620 Hamilton Walk, Philadelphia, PA 19104

Phone Number:  (215) 573-9161

Department

Department: Send Outs

Phone Number: (206) 987-2563

Reference Range

Interpretive report is provided. The probability that a RB1 gene mutation will be detected in an index case depends upon whether the tumor is unilateral or bilateral, unifocal or multi-focal, whether we test tumor or blood, and whether the family history is positive or negative for disease. If the tumor is/was bilateral the sensitivity is ~94% for a germline mutation to be detected. If the tumor is/was unilateral and there is no family history, tumor tissue should be tested first. If tumor is not available, the sensitivity for a germline mutation being present is ~12%. Sensitivity of testing if tumor is provided is ~94%. Deep intronic mutations (non-coding sequences) might not be detected with sequencing. Methylation analysis will be completed on tumor DNA when a second mutation is not identified.

Methodology

Method:

Sequencing: Sanger sequencing of all coding exons and flanking intronic regions of RB1 gene

Deletion/Duplication (Blood): A custom comparative genomic hybridization and single nucleotide polymorphism (CGH + SNP) array designed using Agilent technologies. This high-density array is designed to detect exonic and intronic copy number changes as small as 400 bp and 1.5kb, respectively, in the targeted gene(s). The analysis of the array hybridization data for targeted gene(s) is performed using Cytogenomics software (Agilent Technologies). These results may be confirmed by qPCR.
Note: If a copy number variation occurs that involves the terminal end of the RB1 gene, this assay will expand the analysis to chromosome 13q in order to define breakpoints occurring outside the targeted gene.

Analytical Volume:

Limitations:

Clinical Utility

GeneReviews: Retinoblastoma

Send Out Instructions

Reference Test Name:

Retinoblastoma (RB1):

Sequencing of the coding regions of the RB1 gene with reflex to duplication/deletion analysis [Blood]

 

Reference Test Number: None specified
Instructions: Ship ambient via FedEx. Keep a copy of the requisition for our records. U Penn does NOT accept Saturday delivery.