Laboratory Findings in Multiple Myeloma

Multiple myeloma is associated with more laboratory abnormalities than any other disease. Some of the notable ones are:

Blood

• Peripheral blood smear: normocytic, normochromic anemia, macrocytic anemia, rouleaux formation, neutropenia, thrombocytopenia, abnormal plasma cells (15%)
• High Erythrocyte Sedimentation Rate (ESR)
• High serum total protein and low albumin/globulin ratio
• Septicemia: especially from encapsulated organisms, which are normally cleared by the spleen with the aid of well-functioning antibodies.

Kidney

• Renal failure: ↑ BUN and creatinine, metabolic acidosis
• Anion gap: normal, high or low anion gap
• Nephrotic syndrome: hypoalbuminemia, hyperlipidemia, proteinuria (elevated protein on urine dipstick, elevated urine protein to creatinine ratio), lipiduria (look for Maltese cross formations under polarized light microscopy), peripheral edema
• Proximal (Type 2) renal tubular acidosis: hypokalemia, low urine pH, non-anion gap metabolic acidosis
• Acquired Fanconi syndrome: hypophosphatemia, hypokalemia, Proximal (Type 2) renal tubular acidosis, phosphaturia, aminoaciduria, glucosuria on urinalysis with a normal blood glucose
• Distal (Type 4) renal tubular acidosis: hyperkalemia, non-anion gap metabolic acidosis, ↑ urinary anion gap, ↓ urine pH, ↓ renin, low-normal aldosterone levels and blood pressure

Electrolytes

• ↓ Sodium
• ↑Calcium
• ↑ or ↓ potassium

Other

• ↑ Lactate dehydrogenase (LDH)
• Hypogammaglobulinemia: ↓ levels of normal immunoglobulins IgG, IgA and IgM
• ↑ Alkaline phosphatase: if seen, should make one suspect pathological fractures
• Cryoglobulinemia: proteins, generally immunoglobulins, that precipitate out of solution in low temperatures
• Hyperviscosity (from paraproteinemia, and yes, there is a test for that!)
• Hyperuricemia
• Hyperammonemia
• Endocrinopathies

You confirm the diagnosis with:

•  Serum protein electrophoresis (SPEP) and immunofixation: the SPEP “spike” quantifies the amount of paraprotein, or M-protein, that is coming from a single clone of plasma cells. Immunofixation qualifies the immunoglobulin as IgG, IgA, etc.
• Urine protein electrophoresis (UPEP) and immunofixation
• Serum free light chain assay: Serum free light chains are light chains which are free of heavy chains. This is abnormal when found in the blood in large quantities. Urinary light chains are called Bence-Jones protein
• Skeletal survey (plain radiographs, showing “punched out” lesions)

  

• Bone marrow aspiration and biopsy

Tumor burden is followed by:

• Beta-2 microglobulin
• LDH

References

• The Merck Manual for Health Care Professionals (accessed 5/9/2013)
• Sabatine, Marc S., MD, Pocket Medicine, 4e (2010)
• Victor Hoffbrand, Essential Haematology, 6e (2011)