A 52-year-old male presents with dizziness, fatigue, and low back pain for 3 months. Laboratory tests show Hb 82g/L, WBC 6.2×10<sup>9</sup>/L, PLT 175×10<sup>9</sup>/L, ESR 116mm/h, urinary protein (+), bone marrow plasma cells 52%, M-band on serum protein electrophoresis (SPEP), and L<sub>2</sub>/L<sub>3</sub> vertebral compression fractures on X-ray examination. Which of the following is LEAST likely to be found?