A 54-year-old woman comes to the physician for a 1-month history of worsening pedal edema. She has a 6-month history of back pain. MCV is 108 fL. Serum calcium is 10.4 mEq/L.
Which of the following is the next best step in diagnosis?
Blood smear
Bone marrow biopsy
Flow cytometry
Serum protein electrophoresis
Urinalysis
