Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (376 page)

   Bone marrow clonal plasma cells (usually >10% of nucleated cells) or extramedullary plasmacytoma(s).

   Related organ or tissue impairment (hypercalcemia, renal insufficiency, anemia, bone lesions, amyloidosis, hyperviscosity or recurrent infections).

   Asymptomatic (smoldering) myeloma: patients progress into symptomatic myeloma or amyloidosis at a rate of 10% per year in the first 5 years.

   M protein in serum or urine (>30 g/L IgG, >20 g/L IgA, or >1g/24 hour or urine light chain) and/or

   10% or more clonal plasma cells in bone marrow

   No related organ or tissue impairment

   Laboratory Findings

Laboratory studies are essential for initial diagnosis and prognosis upfront and for determining the presence of a complete remission (CR) following therapy. The current definition of CR is based on serologic and cytologic results, rather than molecular studies.

   
Bone marrow biopsy and aspirate
: Aspirate and biopsy are recommended for identification and quantitation of plasma cells morphologically and by immunophenotype (CD138
⁺
). Plasma cells are seen in sheets or abnormal clusters. Morphology may vary from normal-appearing plasma cells to primitive plasmablasts that may be difficult to identify morphologically.

   
CBC
: Normochromic, normocytic anemia with or without leukopenia, thrombocytopenia, and presence of normoblasts in cases with extensive marrow replacement. Rouleaux formation (due to paraproteinemia) is present on peripheral blood smear (PBS).

   
Serum protein
is markedly elevated with increased globulins and hypoalbuminemia. Decrease in polyclonal gamma globulins is also present and is one of the reasons for repeated infections. Hypogammaglobulinemia in light chain myelomas that produce only light chains.

   
Serum protein electrophoresis and immunofixation
reveal a monoclonal protein (κ or λ) and identify a specific heavy chain (IgG 50%, IgA 20%, IgD, IgE, IgM, and biclonal in <10% of cases). Light chain only is found in 20% of cases (light chain disease).

   
Urine protein electrophoresis and immunofixation
reveal M protein (Bence Jones protein) reflecting urine light chain. With extensive renal damage, albumin and whole immunoglobulin molecules can be found in urine.