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Test Code RB1 Eval RB1 Gene Evaluation

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

 

Notes: Signed informed consent is required.  However, as of 1/1/2016, laboratory genetic counselor at reference lab clarified that we no longer need to have family sign the  "verification of correctly identified tubes" form at time of blood sample collection (page 3 of requistion).

 

Specimen: DNA

Container(s): Sterile plastic tube

Preferred Vol:

Minimum Vol:

 

Notes: Please include the concentration.

 

Specimen: Tumor tissue

Container(s):

Preferred Vol: 5 x 20micron sections (scrolls) if cut paraffin tumor is sent, or frozen tumor

Minimum Vol:

 

Notes: Paraffin tumor can yield an inconclusive result for RB due to the quality of DNA. Specifically, paraffin tumors that have been preserved with picric acid or mercury-containing reagents yield very poor quality DNA.

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

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

Phone Number:  (215) 573-9161

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: RB1 full gene sequencing with automatic reflex to deletion/duplication.  Full sequencing of RB1 gene in DNA isolated from blood or tumor. Deletion/Duplication analysis of RB1 gene in DNA isolated from blood or tumor. 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

 

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.