TEST CATALOG ORDERING & RESULTS SPECIMEN HANDLING CUSTOMER SERVICE EDUCATION & INSIGHTS
Test Catalog

Test ID: COGBL    
Chromosome Analysis, Hematologic Disorders, Children’s Oncology Group Enrollment Testing, Blood

Useful For Suggests clinical disorders or settings where the test may be helpful

Evaluation of pediatric blood specimens for chromosomal abnormalities associated with hematologic malignancies for diagnostic and prognostic purposes in patients being considered for enrollment in Children’s Oncology Group (COG) clinical trials and research protocols

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

This test is only performed on specimens from pediatric patients who are candidates for enrollment in Children's Oncology Group (COG) clinical trials and research protocols.

 

This test includes a charge for cell culture of fresh specimens and professional interpretation of results. Analysis charges will be incurred for total work performed, and generally include 2 banded karyograms and the analysis of 20 metaphase cells. If no metaphase cells are available for analysis, no analysis charges will be incurred. If additional analysis work is required, additional charges may be incurred.

 

-If this test is ordered and the laboratory is informed that the patient is not on a COG protocol, this test will be canceled and automatically reordered as CHRHB / Chromosome Analysis, Hematologic Disorders, Blood.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Clonal chromosomal abnormalities play a central role in the pathogenesis, diagnosis, and treatment monitoring of pediatric hematologic malignancies. Whenever possible, it is best to do chromosome studies for neoplastic hematologic disorders on bone marrow. Bone marrow studies are more sensitive and the chances of finding metaphases are about 95%, compared with only a 60% chance for blood studies. When it is not possible to collect bone marrow, chromosome studies on blood may be useful.

 

When blood cells are cultured in a medium without mitogens, the observation of any chromosomally abnormal clone may be consistent with a neoplastic process.

 

Characteristic chromosome rearrangements and copy number patterns may help classify a pediatric hematologic malignancy. For example, t(1;19)(q23;p13.3) is typically observed in B-lymphoblastic leukemia/lymphoma (B-ALL) and t(8;21)(q22;q22) defines a specific subset of patients with acute myeloid leukemia; while t(7;14)(q35;q11.2) is associated with T-lymphoblastic leukemia/lymphoma. Confirmation of classic gene fusions associated with the above translocations together with evaluation for other recurrent abnormalities are available within the appropriate COG FISH panels; COGBF / B-Lymphoblastic Leukemia/Lymphoma, Children’s Oncology Group Enrollment Testing, FISH, Varies; COGTF / T-Cell Acute Lymphoblastic Leukemia (T-ALL), Children’s Oncology Group Enrollment Testing, FISH, Varies; and COGMF / Acute Myeloid Leukemia (AML), Children’s Oncology Group Enrollment Testing, FISH, Varies. Some rearrangements identified by chromosomal analysis may be extremely rare but are known, recurrent entities for which the Mayo Clinic Genomics Laboratory has the most extensive catalogue of FISH testing to confirm the corollary gene fusions.

 

Metaphase FISH confirmation of classic translocations which are cryptic and not visually detectable by chromosome analysis [ie, t(12;21)] associated with ETV6/RUNX1 fusion) is performed as required by COG and is included as part of the electronic case submission by the Mayo Clinic Genomics Laboratory to COG for central review.

 

Additional cytogenetic techniques such as chromosomal microarray (CMAH / Chromosomal Microarray, Hematologic Disorders, Varies) may be helpful to resolve questions related to ploidy (hyperdiploid clone vs doubled hypodiploid clone) or to resolve certain clonal structural rearrangements such as the presence or absence of intrachromosomal amplification of chromosome 21 (iAMP21). Occasionally, characterization of balanced or complex rearrangements presumed to involve critical genes (such as a kinase activating gene and a fusion partner) may be characterizable by Mate Pair sequencing (MTRBL / MatePair, Targeted Rearrangements, Congenital, Blood); a clinically validated next-generation sequencing technique developed at Mayo Clinic.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

An interpretative report will be provided.

Interpretation Provides information to assist in interpretation of the test results

The presence of an abnormal clone usually indicates a malignant neoplastic process.

 

The absence of an apparent abnormal clone in blood may result from a lack of circulating abnormal cells and not from an absence of disease.

 

On rare occasions, the presence of an abnormality may be associated with a congenital abnormality and, thus, not related to a malignant process. When this situation is suspected, follow-up with a medical genetics consultation is recommended.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Bone marrow specimens are preferred over peripheral blood specimens for the diagnosis of neoplastic hematologic disorders. When peripheral blood must be used, FISH studies may detect some disorders better than conventional chromosome studies.

-FISH studies also may be superior for other hematological disorders when compared to conventional chromosome studies utilizing blood specimens.

 

Interfering factors:

Technical:

-Cell lysis caused by forcing blood quickly through the needle at collection

-Use of an improper anticoagulant (sodium heparin is best) or improperly mixing the blood with the anticoagulant

-Excessive transport time

-Exposure of the specimen to temperature

 

Biological:

-Abnormalities missed due to sampling error

-Subtle structural chromosome abnormalities may not be detected by conventional chromosome analysis

-Neoplastic cells not dividing or not circulating in the bloodstream

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Dewald GW, Ketterling RP, Wyatt WA, Stupca PJ: Cytogenetic studies in neoplastic hematologic disorders. In Clinical Laboratory Medicine, Second edition. Edited by KD McClatchey. Baltimore, Williams and Wilkens, 2002, pp 658-685

2. Rigolin GM, Cibien F, Martinelli S, et al: Chromosome aberrations detected by conventional karyotyping using novel mitogens in chronic lymphocytic leukemia with "normal" FISH: correlations with clinicobiological parameters. Blood 2012 Mar 8;119(10):2310-2313

3. Swerdlow SH, Campo E, Harris NL, et al.: International Agency for Research on Cancer (IARC): World Health Organization (WHO) classification of tumours of haematopoietic and lymphoid tissues. IARC Press, Oxford University Press, 2017

4. Arber DA, Borowitz MJ, Cessna M, et al: Initial Diagnostic Workup of Acute Leukemia: Guideline From the College of American Pathologists and the American Society of Hematology. Arch Pathol Lab Med 2017 Oct;141(10):1342-1393