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Interpretive Handbook

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Test 31141 :
Immunoglobulin Gene Rearrangement, Bone Marrow

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

The immunoglobulin (Ig) genes (heavy, kappa, and lambda) are comprised of numerous, discontinuous coding segments. As B-cells develop, the segments are rearranged such that each mature B-cell and plasma cell has a unique rearrangement profile. Other cell types usually retain the nonrearranged gene structures. Clonal expansion of any B-cell or plasma cell will result in a population of cells that all contain an identical Ig gene rearrangement profile.

 

Reactive B-cell or plasma cell expansions are polyclonal, with each clone containing relatively few cells and no 1 clone predominating. Conversely, neoplastic clones are generally large such that the clonal cells are the predominant B-cells or plasma cells present.

 

In the appropriate clinical and pathologic setting, detection of a prominent Ig gene rearrangement profile may be equated to the presence of a neoplastic B-cell or plasma cell clone.

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

Determining whether a B-cell or plasma cell population is polyclonal or monoclonal

 

Identifying neoplastic cells as having B-cell or plasma cell differentiation

 

Monitoring for a persistent neoplasm by detecting an immunoglobulin gene rearrangement profile similar to 1 from a previous neoplastic specimen

Interpretation Provides information to assist in interpretation of the test results

An interpretive report will be provided.

 

The interpretation of the presence or absence of a predominant immunoglobulin (Ig) gene rearrangement profile is sometimes subjective. These results must always be interpreted in the context of other clinicopathologic information to determine the significance of the result.

 

The detection of a clonal Ig gene rearrangement by this test is not synonymous with the presence of a B-cell or plasma cell neoplasm.

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

This test is neither 100% sensitive nor 100% specific.

 

False-negative results may occur if the immunoglobulin (Ig) gene has numerous point mutations introduced during expansion in a follicle center (somatic hypermutation) such that none of the PCR primers will bind. False-negatives will also occur if the clonal cells have not rearranged the Ig genes being evaluated or are present below the sensitivity level of the assay (sensitivity is quite variable but the assay requires that at least 1%-5% of the nucleated cells present be clonal). False-positive results are rare but may occur if a predominant clone (or small number of clones) is produced or sampled from a polyclonal expansion.

 

The test does not provide information regarding:

-The differentiation of the clonal cell population (neoplastic cells other than B-cells or plasma cells may occasionally have Ig gene rearrangements)

-Whether a prominent clone is physiologic or neoplastic

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 interpretive report will be provided.

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

1. van Dongen JJ, Wolvers-Tettero IL: Analysis of immunoglobulin and T-cell receptor genes. Part II: Possibilities and limitations in the diagnosis and management of lymphoproliferative diseases and related disorders. Clin Chim Acta 1991 April;198(1-2):93-174

2. Coad JE, Olson DJ, Lander TA, et al: Molecular assessment of clonality in lymphoproliferative disorders: I. Immunoglobulin gene rearrangements. Mol Diagn 1996 December;1(4):335-355


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