The updated diagnostic criteria for multiple myeloma include two changes: 1. The addition of biomarkers in addition to the original CRAB features 2. The clarification and updating of laboratory and imaging variables In order to provide physicians and patients and families with a clearer understanding of the progress of the diagnostic criteria for multiple myeloma, we will explain in detail. First, we will look at the definition of bone disease: Multiple myeloma bone disease is defined as the presence of osteolytic bone lesions or the presence of osteoporosis accompanied by compression fractures due to underlying clonal plasma cell disease. In this update of the IMWG criteria, we clarify that one or more findings of osteolytic bone destruction (size ≥5 mm) on CT or PET-CT are clear evidence of meeting the criteria for bone disease in multiple myeloma and should be considered to meet CRAB requirements, regardless of whether they are visible on skeletal radiography. The addition of PET-CT alone is not sufficient to diagnose multiple myeloma; evidence of potentially osteolytic bone destruction regarding the CT portion of this exam is required. Definition of renal failure: Renal impairment is defined in the 2003 IMWG criteria as a serum creatinine concentration above 173 μmol/L (roughly >2 mg/dL) caused by multiple myeloma; this value corresponds to a value 40% above the upper limit of normal serum creatinine. However, to meet the diagnostic criteria for multiple myeloma, a fixed concentration of serum creatinine is used to define renal insufficiency resulting in the need for patients with vastly different degrees of renal impairment based on age, sex, and race. Therefore, the IMWG recommends replacing a fixed serum creatinine concentration with a measured or estimated glomerular filtration rate (based on the Modified Renal Disease Diet [MDRD] or the Collaborative Epidemiologic Study of Chronic Kidney Disease [CKD-EPI] formula) of less than 40 mL/min (equivalent to less than 40% of the lower limit of normal glomerular filtration rate) to meet CRAB criteria.