- Measurable disease at the time of relapse, defined as a monoclonal immunoglobulin spike on serum electrophoresis of >= 1 gm/dL (immunoglobulin [IG]G) or >= 0.5 gm/dL (IGA) and/or urine monoclonal immunoglobulin spike of > 200 mg/24 hours and/ or involved free light chain (FLC) level >= 10 mg/dl and the serum FLC ratio is abnormal