Description

In multiple myeloma there is a clonal proliferation of plasma cells, usually involving the bone marrow. The differential diagnosis includes reactive states or the condition termed monoclonal gammopathy of unknown significance (MGUS). After immunostaining the bone marrow with antibodies to kappa and to lambda light chains, the plasma cells which positively stain can be counted. The relative number of plasma cells staining for kappa vs lambda light chains can help in diagnosis.


 

Specimen: Bone marrow aspirate smears, clot sections or core biopsy.

 

Testing: Each specimen is has one slide immunostained for kappa light chains and one slide immunostained for lambda light chains.

 

Analysis: Plasma cells staining positively were counted in ten 1000-fold magnification fields (10x objective and 100x oil immersion lens).

 

light chain ratio =

= (number of positively staining plasma cells for the predominant light chain) / (number of positively staining plasma cells for the minority light chain

 

Interpretation:

• patients with multiple myeloma had light chain ratios greater than 16

• patients with light chain ratios less than 16 had either a reactive process or monoclonal gammopathy of undetermined significance (MGUS)

 


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