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Interpretive Handbook

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Test 89090 :
Chromosome Analysis, CpG Mitogen Study for B-Cell Disorder

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

Conventional chromosome studies of B-cell disorders are not always successful because B-cell lymphocytes do not proliferate well in cell culture. Fluorescence in situ hybridization (FISH) is an informative method to detect common B-cell-associated chromosome abnormalities, but FISH-based assays do not detect all abnormalities.

 

The agent CpG 7909 (CpG) is a synthetic oligodeoxynucleotide that binds to the Toll-like receptor 9 (TLR9) present on B-cells, causing B-cell activation. In the laboratory setting, CpG may be used as a mitogen to stimulate B-cells in patient specimens, thus allowing identification of chromosome abnormalities.

 

Different disorders have differing levels of response to CpG. In one study, B-cell chronic lymphocytic leukemia (CLL) and marginal zone lymphoma showed the strongest response, followed by small lymphocytic lymphoma, follicular lymphoma, mantle cell lymphoma, and large cell lymphoma.

 

It is likely that CpG-stimulated chromosome analysis and FISH will be complementary tests. For example, about half of the 13q deletions seen in CLL and some lymphomas are microdeletions that are detectable by FISH, but not by conventional metaphase analysis.

 

CpG-stimulation reveals an abnormal karyotype in approximately 80% of patients with B-cell CLL, and the karyotype is complex in 20% to 25% of cases. Several studies have reported that increased genetic complexity revealed by CpG-stimulated chromosome studies confers a less favorable time to first treatment, treatment response, and overall survival.

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

Identifying chromosome abnormalities associated with B-cell disorders

Interpretation Provides information to assist in interpretation of the test results

The abnormalities detected, as well as their known prognostic significance, will be provided in an interpretive report.

 

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.

 

On rare occasions, the presence of an abnormality may be associated with a congenital abnormality and, thus, would not be related to the malignant process. 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

Peripheral blood is preferred over bone marrow.   

 

This test does not replace fluorescence in situ hybridization (FISH) testing as several abnormalities seen by FISH are cryptic (undetected) by conventional chromosome analysis; both FISH and chromosome analysis using CpG 7909 (CpG) cell culture techniques are recommended.

 

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 not mixing the blood with the anticoagulant

-Excessive transport time

-Exposure of the specimen to temperature extremes (freezing or >30 degrees C)

 

Biological

-Abnormalities may be missed due to statistical sampling error

-Subtle structural chromosome abnormalities may be missed (occasionally)

-Neoplastic cells not dividing or not circulating in the bloodstream

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.

46,XX or 46,XY. No apparent chromosome abnormality.

An interpretive report will be provided.

Clinical References Provides recommendations for further in-depth reading of a clinical nature

1. Mayr C, Speicher MR, Kofler DM, et al: Chromosomal translocations are associated with poor prognosis in chronic lymphocytic leukemia. Blood 2006 Jan 15;107(2):742-751

2. Stockero KJ, Fink SR, Smoley SA, et al: Metaphase cells with normal G-bands have cryptic interstitial deletions in 13q14 detectable by fluorescence in situ hybridization in B-cell chronic lymphocytic leukemia. Cancer Genet Cytogenet 2006 Apr 15;166(2):152-156

3. Jahrsdorfer B, Muhlenhoff L, Blackwell SE, et al: B-cell lymphomas differ in their respectiveness to CpG oligodeoxynucleotides. Clin Cancer Res 2005 Feb 15;11(4):1490-1499

4. Dicker F, Schnittger S, Haferlach T, et al: Immunostimulatory oligodeoxynucleotide-induced metaphase cytogenetics detect chromosomal aberrations in 80% of CLL patients: a study of 132 CLL cases with correlation to FISH, IgVH status, and CD38 expression. Blood 2006 Nov 1;108(9):3152-3160

5. Blum KA, Wei L, Jones JA, et al: Activity of combined Flavopiridol and Lenalidomide in patients with cytogenetically high risk chronic lymphocytic leukemia (CLL): Updated results of a Phase I trial. Blood (ASH annual meeting abstracts), Nov 2011;118:3910

6. 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


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