CLINICAL BIOCHEMISTRY DEPARTMENT

LABORATORY INVESTIGATION OF SUSPECTED MYELOMA

Introduction

Investigation of suspected multiple myeloma may be instigated because of clinical findings, such as back or other bone pain; or chance laboratory findings such as low haemoglobin, raised globulin, raised calcium, or unexplained renal impairment.

Diagnosis of myeloma requires at least two of the triad:

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serum paraprotein and/or urine Bence Jones protein

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plasma cell infiltration of bone marrow
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radiological evidence of bone lesions 

Procedure

Initial laboratory investigations should include:

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routine haematology

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biochemistry investigations of renal and bone function

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protein investigations, including serum protein electrophoresis, immunoglobulin assay and urine Bence Jones protein screen. 

Follow up tests will be done automatically depending on the abnormalities found. Paraproteins will be typed and quantitated; positive screening tests for Bence Jones protein will be confirmed; and if required bone marrow studies will be performed by the Haematologists. Radiological investigations will also need to be organised.

Discussion

About 80% of paraproteins - monoclonal immunoglobulins - are due to malignancy, and approximately 65% of these are due to multiple myeloma.  Around 20% of myeloma patients produce only Bence Jones proteins (free light chains) and these are rapidly cleared in the urine in the early stages of the disease, so a urine screen must be done.  Roughly 80% of those with a serum band also have Bence Jones proteinuria.  A few myeloma patients are non-secretors, i.e. they produce no detectable immunoglobulin molecule or fragment.

High paraprotein level, suppression of normal immunoglobulin production, and Bence Jones proteinuria are indicators of a poor prognosis.

Monoclonal immunoglobulins may be seen in other lymphoid cell tumours, as well as in apparently benign cases (MGUS).  The incidence of paraproteinaemia increases with age - it is nearly 10% in those over the age of 80 years.

Faint monoclonal or oligoclonal immunoglobulins may also appear as a transient phenomenon in intense immune reactions.  Usually in these cases, there will also be a raised level of ‘normal’ immunoglobulins. 

 

Reviewed by: John Surrey, Principal Biochemist
Last edited 07/08/08